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76 Commits

Author SHA1 Message Date
Beman Dawes
6f795dce04 Change +++m_count to ++m_count in three places
[SVN r11217]
2001-09-23 12:31:10 +00:00
Beman Dawes
7496ecbc73 sprintf -> std::sprintf + related workarounds
[SVN r11202]
2001-09-22 13:29:58 +00:00
Beman Dawes
76e80ee4c4 Added std:: to size_t in three places
[SVN r11173]
2001-09-20 18:46:11 +00:00
William E. Kempf
8e2536fc54 Updated for new config system.
[SVN r11168]
2001-09-20 14:52:42 +00:00
William E. Kempf
9bbbfbe6ff Fixed some extern "C" bugs.
[SVN r11153]
2001-09-19 17:52:44 +00:00
Beman Dawes
a2fc9ebfaa Fix broken links and other HTML changes related to new config system
[SVN r11142]
2001-09-18 21:24:51 +00:00
William E. Kempf
16c78b81e2 Fixed bug in pthread implementation.
[SVN r11125]
2001-09-14 17:47:09 +00:00
William E. Kempf
e71b204d10 Cleaned up code on warning level 4.
[SVN r11122]
2001-09-14 15:13:12 +00:00
William E. Kempf
f64208ce7a Third round of changes from the review.
[SVN r11109]
2001-09-12 21:29:42 +00:00
Beman Dawes
3410029cad Changes relating to addition of overview.html
[SVN r11103]
2001-09-12 14:38:03 +00:00
Beman Dawes
25fd0f52e7 Initial commit
[SVN r11102]
2001-09-12 14:36:32 +00:00
William E. Kempf
095f16c4f1 Made the constructors inline.
[SVN r11082]
2001-09-10 02:48:20 +00:00
William E. Kempf
5a4a5f405f Fixed bugs in the implementation found during review.
[SVN r11081]
2001-09-10 02:47:46 +00:00
William E. Kempf
7775aceb86 Third changes during review.
[SVN r11049]
2001-09-06 13:11:34 +00:00
William E. Kempf
29177b34a7 Second round of changes during review.
[SVN r11024]
2001-09-05 01:44:20 +00:00
Beman Dawes
ae1c315e0c Fixes after review of Bill's first batch of changes based on Formal Review comments.
[SVN r11021]
2001-09-04 17:16:22 +00:00
William E. Kempf
3592d8c412 First round of modifications during review.
[SVN r11001]
2001-09-03 18:08:35 +00:00
William E. Kempf
63fdf6ef22 Final modifications before submission.
[SVN r10961]
2001-08-30 00:51:17 +00:00
William E. Kempf
915c2cd206 Changed thread design. Updated code and documentation in preperation of submission.
[SVN r10952]
2001-08-28 20:19:37 +00:00
Beman Dawes
54abba952b Event rationale + minor other cleanups
[SVN r10884]
2001-08-17 12:07:35 +00:00
William E. Kempf
7cee797d2e Maded tss class an implementation detail and added thread_specific_ptr template.
[SVN r10873]
2001-08-15 20:49:42 +00:00
William E. Kempf
a7fb1e73d2 Cleaned up code for tss and once methods. Added unit tests for once methods.
[SVN r10838]
2001-08-10 20:47:02 +00:00
Beman Dawes
6a46149868 Added "share stack objects" Q&A
[SVN r10831]
2001-08-10 13:41:58 +00:00
Beman Dawes
f07d726011 Wording clarifications based on comments by Asger Alstrup Nielsen
[SVN r10830]
2001-08-10 12:22:37 +00:00
William E. Kempf
344ddb5fd2 Added tss cleanup functionality and once methods.
[SVN r10827]
2001-08-09 20:32:52 +00:00
Beman Dawes
537b623b18 Add two new questions
[SVN r10820]
2001-08-08 21:07:43 +00:00
Beman Dawes
ab180e79d1 Clarified Memory visibility between threads
[SVN r10798]
2001-08-07 14:45:35 +00:00
Beman Dawes
089dc81880 Major docs workover; use stylesheet, std doc form, show namespace boost in synopsis, rename locks basic_ -> scoped_, etc.
[SVN r10797]
2001-08-06 20:46:24 +00:00
Beman Dawes
73187a40b6 Initial commit
[SVN r10796]
2001-08-06 20:41:47 +00:00
Beman Dawes
3d06b18e3e Renamed from basic_*.html
[SVN r10795]
2001-08-06 20:41:02 +00:00
Beman Dawes
fd9d19b050 Renamed scoped_*.html
[SVN r10794]
2001-08-06 20:39:53 +00:00
William E. Kempf
692aa0e352 Moved lock types into boost::detail::thread. Renamed the lock types. Added locked() methods to lock types.
[SVN r10725]
2001-07-30 18:29:25 +00:00
Beman Dawes
307bbdc951 Format updated.
[SVN r10707]
2001-07-25 20:10:39 +00:00
Beman Dawes
b460053eda Make format consistent with other pages.
[SVN r10706]
2001-07-25 19:38:47 +00:00
Beman Dawes
df704a5dae "basic_lock" -> "scoped_lock" name changes. Added locked() member.
[SVN r10704]
2001-07-25 15:56:43 +00:00
Beman Dawes
9b76b71b5f Changes links format_thread_definition.html -> definitions.html
[SVN r10672]
2001-07-19 20:42:31 +00:00
Beman Dawes
427a109865 Renamed file; was thread_formal_definitions.html
[SVN r10671]
2001-07-19 20:41:30 +00:00
Beman Dawes
5662e2f6bb Remove prior to adding renamed (definitions.html) file
[SVN r10670]
2001-07-19 20:40:40 +00:00
Beman Dawes
6a6fbd0553 Change spelling "thread safe" to "thread-safe" and link to definition of the term. Fix other minor spelling errors.
[SVN r10669]
2001-07-19 20:24:45 +00:00
William E. Kempf
5084e9ccd2 Changed the documentation of basic_lock to describe proper lock() behavior.
Minor modifications to condition.html style.


[SVN r10668]
2001-07-19 18:36:43 +00:00
Beman Dawes
84cb093ee6 basic_lock and related updates
[SVN r10667]
2001-07-19 17:33:12 +00:00
Beman Dawes
8305cad4f8 Add entry, more uniformly apply citation tag
[SVN r10661]
2001-07-18 19:17:47 +00:00
William E. Kempf
b52c5d45ec Added new FAQ questions and cleaned up some documentation.
[SVN r10659]
2001-07-18 14:15:44 +00:00
Beman Dawes
71103fe1bc make wait and timed_wait formatting consistent
[SVN r10655]
2001-07-18 01:16:35 +00:00
Beman Dawes
57d262d4d6 Recast into stanard Boost.Threads doc form (Beman)
[SVN r10651]
2001-07-17 21:22:21 +00:00
Beman Dawes
acf721b0bd Minor changes
[SVN r10650]
2001-07-17 21:17:56 +00:00
William E. Kempf
3ee4bf04dc Fixed minor code changes.
[SVN r10639]
2001-07-16 20:48:39 +00:00
William E. Kempf
6e4a874880 Fixed minor code bugs and changed Jamfiles according to form suggested by Dave Abrahams.
[SVN r10638]
2001-07-16 20:47:48 +00:00
William E. Kempf
b07d60aa94 Updated tss.html for new documentation style. Fixed minor things in thread.html.
[SVN r10637]
2001-07-16 20:04:31 +00:00
William E. Kempf
fb3aed485c Added reference for POSA2.
[SVN r10636]
2001-07-16 18:45:53 +00:00
William E. Kempf
cbf212f1cd Added styles.css. Updated threads.html documentation for new look and design.
[SVN r10635]
2001-07-16 18:24:07 +00:00
Beman Dawes
562c4583d4 Add bibliography link
[SVN r10632]
2001-07-16 15:47:50 +00:00
Beman Dawes
95053b7516 Move Bibliography to separate page, minor tweeks
[SVN r10631]
2001-07-16 15:47:23 +00:00
Beman Dawes
65d06c138e Initial commit
[SVN r10630]
2001-07-16 15:46:04 +00:00
Dave Abrahams
9e3e80558c Repaired.
[SVN r10627]
2001-07-15 19:48:39 +00:00
William E. Kempf
d27e195ca2 Changed code that included exceptions.h to include exceptions.hpp.
[SVN r10601]
2001-07-12 20:36:04 +00:00
William E. Kempf
0ae839e0bb Applied patches for Unix/GNU toolset.
[SVN r10600]
2001-07-12 20:29:43 +00:00
William E. Kempf
21067cb309 Removed extraneous VC++ project files.
[SVN r10560]
2001-07-06 20:13:08 +00:00
Beman Dawes
5cb2a46ae4 Minor wording improvements, more references added
[SVN r10555]
2001-07-06 19:23:45 +00:00
William E. Kempf
66fa1995cf Fixed coding style to match proposed Boost guidelines.
[SVN r10550]
2001-07-06 18:23:40 +00:00
William E. Kempf
6e83cfdc72 Added a FAQ document.
[SVN r10549]
2001-07-06 18:02:56 +00:00
William E. Kempf
c2930faaec Added thread_group documentation.
[SVN r10544]
2001-07-05 19:29:05 +00:00
William E. Kempf
64ad66034a Updated thread documentation to reflect latest design.
[SVN r10543]
2001-07-05 19:11:07 +00:00
William E. Kempf
101e7cfbda Fixed the title.
[SVN r10541]
2001-07-05 18:40:12 +00:00
William E. Kempf
76de0ff7fd Added rationale documentation.
[SVN r10540]
2001-07-05 18:33:05 +00:00
William E. Kempf
f70b32cc63 Modified boost::thread to use a noncopyable design.
[SVN r10519]
2001-07-03 18:29:18 +00:00
William E. Kempf
8ce4eeca24 Changed boost::thread to use a noncopyable design.
[SVN r10518]
2001-07-03 18:28:10 +00:00
William E. Kempf
2febaf386c Modified to use Boost.Function for the threadproc.
[SVN r10437]
2001-06-26 19:20:11 +00:00
William E. Kempf
1d6f10702d Fixed bug (case sensitive subproject name) in jamfiles that prevented building.
[SVN r10434]
2001-06-26 15:40:59 +00:00
William E. Kempf
ebe3a7beee Update all Jamfiles for new build system. (Note: problem with <lib> pseudo-target)
[SVN r10428]
2001-06-25 21:53:57 +00:00
William E. Kempf
9e38dc5f48 Made WinThreads the default for MSVC, as it should have been to begin with.
[SVN r10427]
2001-06-25 21:52:35 +00:00
William E. Kempf
6dafed21fc First attempt at modifying Jamfiles for latest Boost.Build system.
[SVN r10425]
2001-06-25 18:15:31 +00:00
Beman Dawes
067d2a39f7 Integrate new Formal Definition of "Thread" page
[SVN r10365]
2001-06-20 22:49:44 +00:00
Beman Dawes
d70f46126b Replaced by _atomic.cpp
[SVN r10343]
2001-06-15 15:44:13 +00:00
Beman Dawes
b282e06a90 Initial commit
[SVN r10342]
2001-06-15 15:42:45 +00:00
nobody
abd2e68f8d This commit was manufactured by cvs2svn to create branch
'thread-initial'.

[SVN r10341]
2001-06-15 15:42:44 +00:00
234 changed files with 9115 additions and 31197 deletions

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bin*
*.pdb

40
build/Jamfile Normal file
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# (C) Copyright William E. Kempf 2001. Permission to copy, use, modify, sell and
# distribute this software is granted provided this copyright notice appears
# in all copies. This software is provided "as is" without express or implied
# warranty, and with no claim as to its suitability for any purpose.
#
# Boost.Threads build and test Jamfile
#
# Declares the following targets:
# 1. libboost_thread, a static link library.
# 1a. On Win32, a dynamic link library libboost_threadmon,
# which must be used in conjunction with libboost_thread.
# declare the location of this subproject relative to the root
subproject libs/thread/build ;
#######################
#
# Declare the Boost.Threads static link library.
#
# For Win32 we need to build a special DLL, libboost_threadmon, to handle
# TSS destruction.
if $(NT)
{
dll libboost_threadmon : ../src/threadmon.cpp
# requirements
: <threading>multi
: debug release ;
}
# Base names of the source files for libboost_thread
CPP_SOURCES =
condition mutex recursive_mutex semaphore thread tss xtime once ;
lib libboost_thread : ../src/$(CPP_SOURCES).cpp
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;

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@@ -1,208 +0,0 @@
# $Id$
# Copyright 2006-2007 Roland Schwarz.
# Copyright 2007 Anthony Williams
# Distributed under the Boost Software License, Version 1.0. (See
# accompanying file LICENSE_1_0.txt or copy at
# http://www.boost.org/LICENSE_1_0.txt)
#########################################################################
# The boost threading library can be built on top of different API's
# Currently this is the win32 API and the pthreads API.
# Pthread is native on unix variants.
# To get pthread on windows you need the pthread win32 library
# http://sourceware.org/pthreads-win32 which is available under LGPL.
#
# You need to provide the include path and lib path in the variables
# PTW32_INCLUDE and PTW32_LIB respectively. You can specify these
# paths in site-config.jam, user-config.jam or in the environment.
# A new feature is provided to request a specific API:
# <threadapi>win32 and <threadapi)pthread.
#
# The naming of the resulting libraries is mostly the same for the
# variant native to the build platform, i.e.
# boost_thread and the boost specific tagging.
# For the library variant that is not native on the build platform
# an additional tag is applied:
# boost_thread_pthread for the pthread variant on windows, and
# boost_thread_win32 for the win32 variant (likely when built on cygwin).
#
# To request the pthread variant on windows, from boost root you would
# say e.g:
# bjam msvc-8.0 --with-thread install threadapi=pthread
#########################################################################
import os ;
import feature ;
import indirect ;
import path ;
project boost/thread
: source-location ../src
: requirements <threading>multi
<link>static:<define>BOOST_THREAD_BUILD_LIB=1
<link>shared:<define>BOOST_THREAD_BUILD_DLL=1
-<tag>@$(BOOST_JAMROOT_MODULE)%$(BOOST_JAMROOT_MODULE).tag
<tag>@$(__name__).tag
: default-build <threading>multi
;
local rule default_threadapi ( )
{
local api = pthread ;
if [ os.name ] = "NT" { api = win32 ; }
return $(api) ;
}
feature.feature threadapi : pthread win32 : propagated ;
feature.set-default threadapi : [ default_threadapi ] ;
rule tag ( name : type ? : property-set )
{
local result = $(name) ;
if $(type) in STATIC_LIB SHARED_LIB IMPORT_LIB
{
local api = [ $(property-set).get <threadapi> ] ;
# non native api gets additional tag
if $(api) != [ default_threadapi ] {
result = $(result)_$(api) ;
}
}
# forward to the boost tagging rule
return [ indirect.call $(BOOST_JAMROOT_MODULE)%$(BOOST_JAMROOT_MODULE).tag
$(result) : $(type) : $(property-set) ] ;
}
rule win32_pthread_paths ( properties * )
{
local result ;
local PTW32_INCLUDE ;
local PTW32_LIB ;
PTW32_INCLUDE = [ modules.peek : PTW32_INCLUDE ] ;
PTW32_LIB = [ modules.peek : PTW32_LIB ] ;
PTW32_INCLUDE ?= [ modules.peek user-config : PTW32_INCLUDE ] ;
PTW32_LIB ?= [ modules.peek user-config : PTW32_LIB ] ;
PTW32_INCLUDE ?= [ modules.peek site-config : PTW32_INCLUDE ] ;
PTW32_LIB ?= [ modules.peek site-config : PTW32_LIB ] ;
if ! ( $(PTW32_INCLUDE) && $(PTW32_LIB) )
{
if ! $(.notified)
{
echo "************************************************************" ;
echo "Trying to build Boost.Thread with pthread support." ;
echo "If you need pthread you should specify the paths." ;
echo "You can specify them in site-config.jam, user-config.jam" ;
echo "or in the environment." ;
echo "For example:" ;
echo "PTW32_INCLUDE=C:\\Program Files\\ptw32\\Pre-built2\\include" ;
echo "PTW32_LIB=C:\\Program Files\\ptw32\\Pre-built2\\lib" ;
echo "************************************************************" ;
.notified = true ;
}
}
else
{
local include_path = [ path.make $(PTW32_INCLUDE) ] ;
local lib_path = [ path.make $(PTW32_LIB) ] ;
local libname = pthread ;
if <toolset>msvc in $(properties)
{
libname = $(libname)VC2.lib ;
}
if <toolset>gcc in $(properties)
{
libname = lib$(libname)GC2.a ;
}
lib_path = [ path.glob $(lib_path) : $(libname) ] ;
if ! $(lib_path)
{
if ! $(.notified)
{
echo "************************************************************" ;
echo "Trying to build Boost.Thread with pthread support." ;
echo "But the library" $(libname) "could not be found in path" ;
echo $(PTW32_LIB) ;
echo "************************************************************" ;
.notified = true ;
}
}
else
{
result += <include>$(include_path) ;
result += <library>$(lib_path) ;
}
}
return $(result) ;
}
rule usage-requirements ( properties * )
{
local result ;
if <threadapi>pthread in $(properties)
{
result += <define>BOOST_THREAD_POSIX ;
if <target-os>windows in $(properties)
{
result += [ win32_pthread_paths $(properties) ] ;
# TODO: What is for static linking? Is the <library> also needed
# in that case?
}
}
return $(result) ;
}
rule requirements ( properties * )
{
local result ;
if <threadapi>pthread in $(properties)
{
result += <define>BOOST_THREAD_POSIX ;
if <target-os>windows in $(properties)
{
local paths = [ win32_pthread_paths $(properties) ] ;
if $(paths)
{
result += $(paths) ;
}
else
{
result = <build>no ;
}
}
}
return $(result) ;
}
alias thread_sources
: ## win32 sources ##
win32/thread.cpp
win32/exceptions.cpp
win32/tss_dll.cpp
win32/tss_pe.cpp
: ## requirements ##
<threadapi>win32
;
alias thread_sources
: ## pthread sources ##
pthread/thread.cpp
pthread/exceptions.cpp
pthread/once.cpp
: ## requirements ##
<threadapi>pthread
;
explicit thread_sources ;
lib boost_thread
: thread_sources
: <conditional>@requirements
:
: <link>shared:<define>BOOST_THREAD_USE_DLL=1
<link>static:<define>BOOST_THREAD_USE_LIB=1
<conditional>@usage-requirements
;

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# (C) Copyright 2008 Anthony Williams
#
# Distributed under the Boost Software License, Version 1.0. (See accompanying
# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
path-constant boost-images : ../../../doc/src/images ;
xml thread : thread.qbk ;
boostbook standalone
:
thread
:
# HTML options first:
# Use graphics not text for navigation:
<xsl:param>navig.graphics=1
# How far down we chunk nested sections, basically all of them:
<xsl:param>chunk.section.depth=3
# Don't put the first section on the same page as the TOC:
<xsl:param>chunk.first.sections=1
# How far down sections get TOC's
<xsl:param>toc.section.depth=10
# Max depth in each TOC:
<xsl:param>toc.max.depth=3
# How far down we go with TOC's
<xsl:param>generate.section.toc.level=10
# Path for links to Boost:
<xsl:param>boost.root=../../../..
# Path for libraries index:
<xsl:param>boost.libraries=../../../../libs/libraries.htm
# Use the main Boost stylesheet:
<xsl:param>html.stylesheet=../../../../doc/html/boostbook.css
# PDF Options:
# TOC Generation: this is needed for FOP-0.9 and later:
#<xsl:param>fop1.extensions=1
# Or enable this if you're using XEP:
<xsl:param>xep.extensions=1
# TOC generation: this is needed for FOP 0.2, but must not be set to zero for FOP-0.9!
<xsl:param>fop.extensions=0
# No indent on body text:
<xsl:param>body.start.indent=0pt
# Margin size:
<xsl:param>page.margin.inner=0.5in
# Margin size:
<xsl:param>page.margin.outer=0.5in
# Yes, we want graphics for admonishments:
<xsl:param>admon.graphics=1
# Set this one for PDF generation *only*:
# default pnd graphics are awful in PDF form,
# better use SVG's instead:
<format>pdf:<xsl:param>admon.graphics.extension=".svg"
<format>pdf:<xsl:param>admon.graphics.path=$(boost-images)/
;

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doc/acknowledgements.html Normal file
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost.Threads Acknowledgements</title>
</head>
<body bgcolor="#FFFFFF" text="#000000">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Acknowledgements</h2>
</td>
</tr>
</table>
<h2>Acknowledgments</h2>
<p><a href="../../../people/william_kempf.htm">William E. Kempf</a> was the
architect, designer, and implementor of <b>Boost.Threads</b>.</p>
<p>Important contributions were also made by Jeremy Siek (lots of input on
the design and on the implementation), Alexander Terekhov (lots of input on
the Win32 implementation, especially in regards to boost::condition, as well
as a lot of explanation of POSIX behavior), Greg Colvin (lots of input on the
design), and Paul Mclachlan, Thomas Matelich and Iain Hanson (for help in
trying to get the build to work on other platforms).</p>
<p>The documentation was written by William E. Kempf. Beman Dawes provided
additional documentation material and editing.</p>
<p>Discussions on the boost.org mailing list were essential in the development
of <b>Boost.Threads</b>. As of August 1, 2001, participants included Alan Griffiths,
Albrecht Fritzsche, Aleksey Gurtovoy, Alexander Terekhov, Andrew Green, Andy Sawyer,
Asger Alstrup Nielsen, Beman Dawes, Bill Klein, Bill Rutiser, Bill Wade, Branko
Èibej, Brent Verner, Craig Henderson, Csaba Szepesvari, Dale Peakall, Damian
Dixon, Dan Nuffer, Darryl Green, Daryle Walker, David Abrahams, David Allan
Finch, Dejan Jelovic, Dietmar Kuehl, Doug Gregor, Douglas Gregor, Duncan Harris,
Ed Brey, Eric Swanson, Eugene Karpachov, Fabrice Truillot, Frank
Gerlach, Gary Powell, Gernot Neppert, Geurt Vos, Ghazi Ramadan, Greg Colvin,
Gregory Seidman, HYS, Iain Hanson, Ian Bruntlett, J Panzer, Jeff Garland, Jeff
Paquette, Jens Maurer, Jeremy Siek, Jesse Jones, Joe Gottman, John (EBo) David,
John Bandela, John Maddock, John Max Skaller, John Panzer, Jon Jagger , Karl
Nelson, Kevlin Henney, KG Chandrasekhar, Levente Farkas, Lie-Quan Lee, Lois
Goldthwaite, Luis Pedro Coelho, Marc Girod, Mark A. Borgerding, Mark Rodgers,
Marshall Clow, Matthew Austern, Matthew Hurd, Michael D. Crawford, Michael H.
Cox , Mike Haller, Miki Jovanovic, Nathan Myers, Paul Moore, Pavel Cisler, Peter
Dimov, Petr Kocmid, Philip Nash, Rainer Deyke, Reid Sweatman, Ross Smith, Scott
McCaskill, Shalom Reich , Steve Cleary, Steven Kirk, Thomas Holenstein, Thomas
Matelich, Trevor Perrin, Valentin Bonnard, Vesa Karvonen, Wayne Miller, and
William Kempf.</p>
<p>Apologies for anyone inadvertently missed.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->29 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34360" -->
</p>
<p>©<i> Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001</i></p>
</body>
</html>

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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:acknowledgements Acknowledgments]
The original implementation of __boost_thread__ was written by William Kempf, with contributions from numerous others. This new
version initially grew out of an attempt to rewrite __boost_thread__ to William Kempf's design with fresh code that could be
released under the Boost Software License. However, as the C++ Standards committee have been actively discussing standardizing a
thread library for C++, this library has evolved to reflect the proposals, whilst retaining as much backwards-compatibility as
possible.
Particular thanks must be given to Roland Schwarz, who contributed a lot of time and code to the original __boost_thread__ library,
and who has been actively involved with the rewrite. The scheme for dividing the platform-specific implementations into separate
directories was devised by Roland, and his input has contributed greatly to improving the quality of the current implementation.
Thanks also must go to Peter Dimov, Howard Hinnant, Alexander Terekhov, Chris Thomasson and others for their comments on the
implementation details of the code.
[endsect]

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.acknowledgements"
last-revision="$Date$">
<title>Acknowledgements</title>
<para>William E. Kempf was the architect, designer, and implementor of
&Boost.Thread;.</para>
<para>Mac OS Carbon implementation written by Mac Murrett.</para>
<para>Dave Moore provided initial submissions and further comments on the
<code>barrier</code>
,
<code>thread_pool</code>
,
<code>read_write_mutex</code>
,
<code>read_write_try_mutex</code>
and
<code>read_write_timed_mutex</code>
classes.</para>
<para>Important contributions were also made by Jeremy Siek (lots of input
on the design and on the implementation), Alexander Terekhov (lots of input
on the Win32 implementation, especially in regards to boost::condition, as
well as a lot of explanation of POSIX behavior), Greg Colvin (lots of input
on the design), Paul Mclachlan, Thomas Matelich and Iain Hanson (for help
in trying to get the build to work on other platforms), and Kevin S. Van
Horn (for several updates/corrections to the documentation).</para>
<para>Mike Glassford finished changes to &Boost.Thread; that were begun
by William Kempf and moved them into the main CVS branch.
He also addressed a number of issues that were brought up on the Boost
developer's mailing list and provided some additions and changes to the
read_write_mutex and related classes.</para>
<para>The documentation was written by William E. Kempf. Beman Dawes
provided additional documentation material and editing.
Mike Glassford finished William Kempf's conversion of the documentation to
BoostBook format and added a number of new sections.</para>
<para>Discussions on the boost.org mailing list were essential in the
development of &Boost.Thread;
. As of August 1, 2001, participants included Alan Griffiths, Albrecht
Fritzsche, Aleksey Gurtovoy, Alexander Terekhov, Andrew Green, Andy Sawyer,
Asger Alstrup Nielsen, Beman Dawes, Bill Klein, Bill Rutiser, Bill Wade,
Branko &egrave;ibej, Brent Verner, Craig Henderson, Csaba Szepesvari,
Dale Peakall, Damian Dixon, Dan Nuffer, Darryl Green, Daryle Walker, David
Abrahams, David Allan Finch, Dejan Jelovic, Dietmar Kuehl, Douglas Gregor,
Duncan Harris, Ed Brey, Eric Swanson, Eugene Karpachov, Fabrice Truillot,
Frank Gerlach, Gary Powell, Gernot Neppert, Geurt Vos, Ghazi Ramadan, Greg
Colvin, Gregory Seidman, HYS, Iain Hanson, Ian Bruntlett, J Panzer, Jeff
Garland, Jeff Paquette, Jens Maurer, Jeremy Siek, Jesse Jones, Joe Gottman,
John (EBo) David, John Bandela, John Maddock, John Max Skaller, John
Panzer, Jon Jagger , Karl Nelson, Kevlin Henney, KG Chandrasekhar, Levente
Farkas, Lie-Quan Lee, Lois Goldthwaite, Luis Pedro Coelho, Marc Girod, Mark
A. Borgerding, Mark Rodgers, Marshall Clow, Matthew Austern, Matthew Hurd,
Michael D. Crawford, Michael H. Cox , Mike Haller, Miki Jovanovic, Nathan
Myers, Paul Moore, Pavel Cisler, Peter Dimov, Petr Kocmid, Philip Nash,
Rainer Deyke, Reid Sweatman, Ross Smith, Scott McCaskill, Shalom Reich,
Steve Cleary, Steven Kirk, Thomas Holenstein, Thomas Matelich, Trevor
Perrin, Valentin Bonnard, Vesa Karvonen, Wayne Miller, and William
Kempf.</para>
<para>
As of February 2006 Anthony Williams and Roland Schwarz took over maintainance
and further development of the library after it has been in an orphaned state
for a rather long period of time.
</para>
<para>Apologies for anyone inadvertently missed.</para>
</section>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/barrier.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="barrier">
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<purpose>
<para>An object of class <classname>barrier</classname> is a synchronization
primitive used to cause a set of threads to wait until they each perform a
certain function or each reach a particular point in their execution.</para>
</purpose>
<description>
<para>When a barrier is created, it is initialized with a thread count N.
The first N-1 calls to <code>wait()</code> will all cause their threads to be blocked.
The Nth call to <code>wait()</code> will allow all of the waiting threads, including
the Nth thread, to be placed in a ready state. The Nth call will also "reset"
the barrier such that, if an additional N+1th call is made to <code>wait()</code>,
it will be as though this were the first call to <code>wait()</code>; in other
words, the N+1th to 2N-1th calls to <code>wait()</code> will cause their
threads to be blocked, and the 2Nth call to <code>wait()</code> will allow all of
the waiting threads, including the 2Nth thread, to be placed in a ready state
and reset the barrier. This functionality allows the same set of N threads to re-use
a barrier object to synchronize their execution at multiple points during their
execution.</para>
<para>See <xref linkend="thread.glossary"/> for definitions of thread
states <link linkend="thread.glossary.thread-state">blocked</link>
and <link linkend="thread.glossary.thread-state">ready</link>.
Note that "waiting" is a synonym for blocked.</para>
</description>
<constructor>
<parameter name="count">
<paramtype>size_t</paramtype>
</parameter>
<effects><simpara>Constructs a <classname>barrier</classname> object that
will cause <code>count</code> threads to block on a call to <code>wait()</code>.
</simpara></effects>
</constructor>
<destructor>
<effects><simpara>Destroys <code>*this</code>. If threads are still executing
their <code>wait()</code> operations, the behavior for these threads is undefined.
</simpara></effects>
</destructor>
<method-group name="waiting">
<method name="wait">
<type>bool</type>
<effects><simpara>Wait until N threads call <code>wait()</code>, where
N equals the <code>count</code> provided to the constructor for the
barrier object.</simpara>
<simpara><emphasis role="bold">Note</emphasis> that if the barrier is
destroyed before <code>wait()</code> can return, the behavior is
undefined.</simpara></effects>
<returns>Exactly one of the N threads will receive a return value
of <code>true</code>, the others will receive a value of <code>false</code>.
Precisely which thread receives the return value of <code>true</code> will
be implementation-defined. Applications can use this value to designate one
thread as a leader that will take a certain action, and the other threads
emerging from the barrier can wait for that action to take place.</returns>
</method>
</method-group>
</class>
</namespace>
</header>

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@@ -1,72 +0,0 @@
[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:barriers Barriers]
A barrier is a simple concept. Also known as a ['rendezvous], it is a synchronization point between multiple threads. The barrier is
configured for a particular number of threads (`n`), and as threads reach the barrier they must wait until all `n` threads have
arrived. Once the `n`-th thread has reached the barrier, all the waiting threads can proceed, and the barrier is reset.
[section:barrier Class `barrier`]
#include <boost/thread/barrier.hpp>
class barrier
{
public:
barrier(unsigned int count);
~barrier();
bool wait();
};
Instances of __barrier__ are not copyable or movable.
[heading Constructor]
barrier(unsigned int count);
[variablelist
[[Effects:] [Construct a barrier for `count` threads.]]
[[Throws:] [__thread_resource_error__ if an error occurs.]]
]
[heading Destructor]
~barrier();
[variablelist
[[Precondition:] [No threads are waiting on `*this`.]]
[[Effects:] [Destroys `*this`.]]
[[Throws:] [Nothing.]]
]
[heading Member function `wait`]
bool wait();
[variablelist
[[Effects:] [Block until `count` threads have called `wait` on `*this`. When the `count`-th thread calls `wait`, all waiting threads
are unblocked, and the barrier is reset. ]]
[[Returns:] [`true` for exactly one thread from each batch of waiting threads, `false` otherwise.]]
[[Throws:] [__thread_resource_error__ if an error occurs.]]
]
[endsect]
[endsect]

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost.Threads Bibliography</title>
</head>
<body bgcolor="#FFFFFF" text="#000000">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Bibliography</h2>
</td>
</tr>
</table>
<h2>Bibliography</h2>
<table border="0" cellpadding="5" width="777">
<tr>
<td width="102" valign="top" align="left"><b>[<a name="Andrews-83">Andrews
83</a>]</b></td>
<td width="645">
Gregory R. Andrews, Fred B. Schneider, <cite>Concepts and Notations for Concurrent
Programming</cite>, ACM Computing Surveys, Vol. 15, No. 1, March, 1983. <a href="http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/">http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/</a>
<p>Good general background reading.&nbsp; Includes descriptions of Path
Expressions, Message Passing, and Remote Procedure Call in addition to the
basics.&nbsp;
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name="Boost">Boost</a>]</b></td>
<td width="645">
The <cite> Boost</cite> world-wide web site.&nbsp; <a href="http://www.boost.org">http://www.boost.org</a>
<p>Boost.Threads is one of many Boost libraries.&nbsp; The Boost web site
includes a great deal of documentation and general information which applies to
all Boost libraries. Current copies of the libraries including documentation and
test programs may be downloaded from the web site.
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name="Brinch-Hansen-73">Brinch
Hansen 73</a>]</b></td>
<td width="645">
Per Brinch Hansen, <cite>Concurrent Programming Concepts</cite>, ACM Computing
Surveys, Vol. 5, No. 4, December, 1973. <a href="http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/p223-hansen.pdf">http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/</a>
<p>&quot;This paper describes the evolution of language features for
multiprogramming from event queues and semaphores to critical regions and
monitors.&quot; Includes analysis of&nbsp; why <i>events</i> are considered
error-prone. Also noteworthy because of an introductory quotation from
Christopher Alexander; Brinch Hansen was years ahead of others in recognizing
pattern concepts applied to software too.
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>]<a name="Butenhof-97">Butenhof
97</a>]</b></td>
<td width="645">
<p> David R. Butenhof, <cite>Programming with
POSIX Threads</cite>, Addison-Wesley 1997, ISBN 0-201-63392-2&nbsp; <a href="http://cseng.aw.com/book/0,3828,0201633922,00.html">http://cseng.aw.com/book/0,3828,0201633922,00.html</a></p>
<p>This is a very readable explanation of threads and how to use them.&nbsp; Many
of the insights given apply to all multi-threaded programming, not just POSIX
Threads.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name="Hoare-74">Hoare 74</a>]</b></td>
<td width="645">
<p>C.A.R Hoare, <cite> Monitors: An Operating System Structuring Concept</cite>,
Communications of the ACM, Vol. 17, No. 10. October
1974, pp. 549-557&nbsp; <a href="http://www.acm.org/classics/feb96/">http://www.acm.org/classics/feb96/ </a></p>
<p>Hoare and Brinch Hansen's work on Monitors is the basis for reliable
multi-threading patterns. This is one of the most often referenced papers in
all of computer science, and with good reason.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name="ISO-98">ISO 98</a>]</b></td>
<td width="645">
<p>ISO/IEC 14882:1998(E) <cite> Programming Language C++</cite>&nbsp; <a href="http://www.ansi.org">http://www.ansi.org</a></p>
<p>This is the official C++ Standards
document. Available from the ANSI (American
National Standards Institute) Electronic Standards Store.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name="McDowell-89">McDowell
89</a>]</b></td>
<td width="645">
Charles E McDowell, David P. Helmbold, <cite>Debugging Concurrent Programs</cite>,
ACM Computing Surveys, Vol. 21, No. 2, December, 1989. <a href="http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/">http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/</a>
<p>Identifies many of the unique failure modes and debugging difficulties
associated with concurrent programs.
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"> <b>[<a name="Schmidt">Schmidt</a>]&nbsp;</b></td>
<td width="645">
<p> Douglas C. Schmidt and Irfan Pyarali, <cite>Strategies for
Implementing POSIX Condition Variables on Win32</cite>,&nbsp; Department of Computer Science, Washington University, St. Louis, Missouri.&nbsp;
<a href="http://www.cs.wustl.edu/~schmidt/win32-cv-1.html">http://www.cs.wustl.edu/~schmidt/win32-cv-1.html</a></p>
<p>Rationale for understanding Boost.Threads condition variables. Note that Alexander Terekhov found some bugs in
the implementation given in this article, so pthreads-win32 and Boost.Threads
are even more complicated yet.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"> <b>[<a name="Schmidt-00">Schmidt
00</a>]&nbsp;</b></td>
<td width="645">
<p> Douglas C. Schmidt, Michael Stal, Hans Rohnert and Frank Buschmann, <cite>Pattern-Oriented Software Architecture Volume 2 - Patterns for
Concurrent and Networked Objects</cite>,&nbsp; Wiley 2000, ISBN 0-471-60695-2&nbsp; <a href="http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html">http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html</a></p>
<p>This is a very good explanation of how to apply several patterns useful for concurrent programming.
Among the patterns documented is the Monitor Pattern mentioned frequently in the <b>Boost.Threads</b>
documentation.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"> <b>[<a name="Stroustrup-00">Stroustrup
00</a>]</b></td>
<td width="645">
Bjarne Stroustrup, <cite> The C++ Programming Language</cite>, Special Edition, Addison-Wesley
2000, ISBN 0-201-70073-5 <a href="http://cseng.aw.com/book/0,3828,0201700735,00.html">http://cseng.aw.com/book/0,3828,0201700735,00.html</a>
<p>The first book a C++ programmer should own.&nbsp; Note that the 3rd edition
(and subsequent editions like the Special Edition) has been rewritten to cover
the ISO standard language and library.
</td>
</tr>
</table>
<p>Note: The URL's above are provided in plain text form so that they will be visible
on printed copies of this document.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %b %Y" startspan -->17 Aug 2001<!--webbot bot="Timestamp" endspan i-checksum="14763" -->
</p>
<p>© Copyright Beman Dawes, 2001</p>
</body>
</html>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<bibliography id="thread.bibliography"
last-revision="$Date$">
<title>Bibliography</title>
<biblioentry id="thread.bib.AndrewsSchneider83">
<abbrev id="thread.bib.AndrewsSchneider83.abbrev">AndrewsSchnieder83</abbrev>
<biblioset relation="journal">
<title>ACM Computing Surveys</title>
<volumenum>Vol. 15</volumenum>
<issuenum>No. 1</issuenum>
<date>March, 1983</date>
</biblioset>
<biblioset relation="article">
<authorgroup>
<author>
<firstname>Gregory</firstname>
<othername>R.</othername>
<surname>Andrews</surname>
</author>
<author>
<firstname>Fred</firstname>
<othername>B.</othername>
<surname>Schneider</surname>
</author>
</authorgroup>
<title>
<ulink
url="http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/"
>Concepts and Notations for Concurrent Programming</ulink>
</title>
</biblioset>
<para>Good general background reading. Includes descriptions of Path
Expressions, Message Passing, and Remote Procedure Call in addition to the
basics</para>
</biblioentry>
<biblioentry id="thread.bib.Boost">
<abbrev id="thread.bib.Boost.abbrev">Boost</abbrev>
<bibliomisc>The <emphasis>Boost</emphasis> world wide web site.
<ulink url="http:/www.boost.org">http://www.boost.org</ulink></bibliomisc>
<para>&Boost.Thread; is one of many Boost libraries. The Boost web
site includes a great deal of documentation and general information which
applies to all Boost libraries. Current copies of the libraries including
documentation and test programs may be downloaded from the web
site.</para>
</biblioentry>
<biblioentry id="thread.bib.Hansen73">
<abbrev id="thread.bib.Hansen73.abbrev">Hansen73</abbrev>
<biblioset relation="journal">
<title>ACM Computing Surveys</title>
<volumenum>Vol. 5</volumenum>
<issuenum>No. 4</issuenum>
<date>December, 1973</date>
</biblioset>
<biblioset relation="article">
<author>0-201-63392-2
<firstname>Per Brinch</firstname>
<lastname>Hansen</lastname>
</author>
<title>
<ulink
url="http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/"
>Concurrent Programming Concepts</ulink>
</title>
</biblioset>
<para>"This paper describes the evolution of language features for
multiprogramming from event queues and semaphores to critical regions and
monitors." Includes analysis of why events are considered error-prone. Also
noteworthy because of an introductory quotation from Christopher Alexander;
Brinch Hansen was years ahead of others in recognizing pattern concepts
applied to software, too.</para>
</biblioentry>
<biblioentry id="thread.bib.Butenhof97">
<abbrev id="thread.bib.Butenhof97.abbrev">Butenhof97</abbrev>
<title>
<ulink url="http://cseng.aw.com/book/0,3828,0201633922,00.html"
>Programming with POSIX Threads </ulink>
</title>
<author>
<firstname>David</firstname>
<othername>R.</othername>
<surname>Butenhof</surname>
</author>
<publisher>Addison-Wesley</publisher>
<copyright><year>1997</year></copyright>
<isbn>ISNB: 0-201-63392-2</isbn>
<para>This is a very readable explanation of threads and how to use
them. Many of the insights given apply to all multithreaded programming, not
just POSIX Threads</para>
</biblioentry>
<biblioentry id="thread.bib.Hoare74">
<abbrev id="thread.bib.Hoare74.abbrev">Hoare74</abbrev>
<biblioset relation="journal">
<title>Communications of the ACM</title>
<volumenum>Vol. 17</volumenum>
<issuenum>No. 10</issuenum>
<date>October, 1974</date>
</biblioset>
<biblioset relation="article">
<title>
<ulink url=" http://www.acm.org/classics/feb96/"
>Monitors: An Operating System Structuring Concept</ulink>
</title>
<author>
<firstname>C.A.R.</firstname>
<surname>Hoare</surname>
</author>
<pagenums>549-557</pagenums>
</biblioset>
<para>Hoare and Brinch Hansen's work on Monitors is the basis for reliable
multithreading patterns. This is one of the most often referenced papers in
all of computer science, and with good reason.</para>
</biblioentry>
<biblioentry id="thread.bib.ISO98">
<abbrev id="thread.bib.ISO98.abbrev">ISO98</abbrev>
<title>
<ulink url="http://www.ansi.org">Programming Language C++</ulink>
</title>
<orgname>ISO/IEC</orgname>
<releaseinfo>14882:1998(E)</releaseinfo>
<para>This is the official C++ Standards document. Available from the ANSI
(American National Standards Institute) Electronic Standards Store.</para>
</biblioentry>
<biblioentry id="thread.bib.McDowellHelmbold89">
<abbrev id="thread.bib.McDowellHelmbold89.abbrev">McDowellHelmbold89</abbrev>
<biblioset relation="journal">
<title>Communications of the ACM</title>
<volumenum>Vol. 21</volumenum>
<issuenum>No. 2</issuenum>
<date>December, 1989</date>
</biblioset>
<biblioset>
<author>
<firstname>Charles</firstname>
<othername>E.</othername>
<surname>McDowell</surname>
</author>
<author>
<firstname>David</firstname>
<othername>P.</othername>
<surname>Helmbold</surname>
</author>
<title>
<ulink
url="http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/"
>Debugging Concurrent Programs</ulink>
</title>
</biblioset>
<para>Identifies many of the unique failure modes and debugging difficulties
associated with concurrent programs.</para>
</biblioentry>
<biblioentry id="thread.bib.SchmidtPyarali">
<abbrev id="thread.bib.SchmidtPyarali.abbrev">SchmidtPyarali</abbrev>
<title>
<ulink url="http://www.cs.wustl.edu/~schmidt/win32-cv-1.html8"
>Strategies for Implementing POSIX Condition Variables on Win32</ulink>
</title>
<authorgroup>
<author>
<firstname>Douglas</firstname>
<othername>C.</othername>
<surname>Schmidt</surname>
</author>
<author>
<firstname>Irfan</firstname>
<surname>Pyarali</surname>
</author>
</authorgroup>
<orgname>Department of Computer Science, Washington University, St. Louis,
Missouri</orgname>
<para>Rationale for understanding &Boost.Thread; condition
variables. Note that Alexander Terekhov found some bugs in the
implementation given in this article, so pthreads-win32 and &Boost.Thread;
are even more complicated yet.</para>
</biblioentry>
<biblioentry id="thread.bib.SchmidtStalRohnertBuschmann">
<abbrev
id="thread.bib.SchmidtStalRohnertBuschmann.abbrev">SchmidtStalRohnertBuschmann</abbrev>
<title>
<ulink
url="http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html"
>Pattern-Oriented Architecture Volume 2</ulink>
</title>
<subtitle>Patterns for Concurrent and Networked Objects</subtitle>
<titleabbrev>POSA2</titleabbrev>
<authorgroup>
<author>
<firstname>Douglas</firstname>
<othername>C.</othername>
<surname>Schmidt</surname>
</author>
<author>
<firstname>Michael</firstname>
<lastname>Stal</lastname>
</author>
<author>
<firstname>Hans</firstname>
<surname>Rohnert</surname>
</author>
<author>
<firstname>Frank</firstname>
<surname>Buschmann</surname>
</author>
</authorgroup>
<publisher>Wiley</publisher>
<copyright><year>2000</year></copyright>
<para>This is a very good explanation of how to apply several patterns
useful for concurrent programming. Among the patterns documented is the
Monitor Pattern mentioned frequently in the &Boost.Thread;
documentation.</para>
</biblioentry>
<biblioentry id="thread.bib.Stroustrup">
<abbrev id="thread.bib.Stroustrup.abbrev">Stroustrup</abbrev>
<title>
<ulink url="http://cseng.aw.com/book/0,3828,0201700735,00.html"
>The C++ Programming Language</ulink>
</title>
<edition>Special Edition</edition>
<publisher>Addison-Wesley</publisher>
<copyright><year>2000</year></copyright>
<isbn>ISBN: 0-201-70073-5</isbn>
<para>The first book a C++ programmer should own. Note that the 3rd edition
(and subsequent editions like the Special Edition) has been rewritten to
cover the ISO standard language and library.</para>
</biblioentry>
</bibliography>

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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Copyright (c) 2007 Roland Schwarz
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.build" last-revision="$Date$">
<title>Build</title>
<para>
How you build the &Boost.Thread; libraries, and how you build your own applications
that use those libraries, are some of the most frequently asked questions. Build
processes are difficult to deal with in a portable manner. That's one reason
why &Boost.Thread; makes use of &Boost.Build;.
In general you should refer to the documentation for &Boost.Build;.
This document will only supply you with some simple usage examples for how to
use <emphasis>bjam</emphasis> to build and test &Boost.Thread;. In addition, this document
will try to explain the build requirements so that users may create their own
build processes (for instance, create an IDE specific project), both for building
and testing &Boost.Thread;, as well as for building their own projects using
&Boost.Thread;.
</para>
<section id="thread.build.building">
<title>Building the &Boost.Thread; Libraries</title>
<para>
Building the &Boost.Thread; Library depends on how you intend to use it. You have several options:
<itemizedlist>
<listitem>
Using as a <link linkend="thread.build.precompiled">precompiled</link> library, possibly
with auto-linking, or for use from within an IDE.
</listitem>
<listitem>
Use from a <link linkend="thread.build.bjam">&Boost.Build;</link> project.
</listitem>
<listitem>
Using in <link linkend="thread.build.source">source</link> form.
</listitem>
</itemizedlist>
</para>
<section id="thread.build.precompiled">
<title>Precompiled</title>
<para>
Using the &Boost.Thread; library in precompiled form is the way to go if you want to
install the library to a standard place, from where your linker is able to resolve code
in binary form. You also will want this option if compile time is a concern. Multiple
variants are available, for different toolsets and build variants (debug/release).
The library files are named <emphasis>{lead}boost_thread{build-specific-tags}.{extension}</emphasis>,
where the build-specific-tags indicate the toolset used to build the library, whether it's
a debug or release build, what version of &Boost; was used, etc.; and the lead and extension
are the appropriate extensions for a dynamic link library or static library for the platform
for which &Boost.Thread; is being built.
For instance, a debug build of the dynamic library built for Win32 with VC++ 7.1 using Boost 1.34 would
be named <emphasis>boost_thread-vc71-mt-gd-1_34.dll</emphasis>.
More information on this should be available from the &Boost.Build; documentation.
</para>
<para>
Building should be possible with the default configuration. If you are running into problems,
it might be wise to adjust your local settings of &Boost.Build; though. Typically you will
need to get your user-config.jam file to reflect your environment, i.e. used toolsets. Please
refer to the &Boost.Build; documentation to learn how to do this.
</para>
<para>
To create the libraries you need to open a command shell and change to the
<emphasis>boost_root</emphasis> directory. From there you give the command
<programlisting>bjam --toolset=<emphasis>mytoolset</emphasis> stage --with-thread</programlisting>
Replace <emphasis>mytoolset</emphasis> with the name of your toolset, e.g. msvc-7.1 .
This will compile and put the libraries into the <emphasis>stage</emphasis> directory which is just below the
<emphasis>boost_root</emphasis> directory. &Boost.Build; by default will generate static and
dynamic variants for debug and release.
</para>
<note>
Invoking the above command without the --with-thread switch &Boost.Build; will build all of
the Boost distribution, including &Boost.Thread;.
</note>
<para>
The next step is to copy your libraries to a place where your linker is able to pick them up.
It is also quite possible to leave them in the stage directory and instruct your IDE to take them
from there.
</para>
<para>
In your IDE you then need to add <emphasis>boost_root</emphasis>/boost to the paths where the compiler
expects to find files to be included. For toolsets that support <emphasis>auto-linking</emphasis>
it is not necessary to explicitly specify the name of the library to link against, it is sufficient
to specify the path of the stage directory. Typically this is true on Windows. For gcc you need
to specify the exact library name (including all the tags). Please don't forget that threading
support must be turned on to be able to use the library. You should be able now to build your
project from the IDE.
</para>
</section>
<section id="thread.build.bjam">
<title>&Boost.Build; Project</title>
<para>
If you have decided to use &Boost.Build; as a build environment for your application, you simply
need to add a single line to your <emphasis>Jamroot</emphasis> file:
<programlisting>use-project /boost : {path-to-boost-root} ;</programlisting>
where <emphasis>{path-to-boost-root}</emphasis> needs to be replaced with the location of
your copy of the boost tree.
Later when you specify a component that needs to link against &Boost.Thread; you specify this
as e.g.:
<programlisting>exe myapp : {myappsources} /boost//thread ;</programlisting>
and you are done.
</para>
</section>
<section id="thread.build.source">
<title>Source Form</title>
<para>
Of course it is also possible to use the &Boost.Thread; library in source form.
First you need to specify the <emphasis>boost_root</emphasis>/boost directory as
a path where your compiler expects to find files to include. It is not easy
to isolate the &Boost.Thread; include files from the rest of the boost
library though. You would also need to isolate every include file that the thread
library depends on. Next you need to copy the files from
<emphasis>boost_root</emphasis>/libs/thread/src to your project and instruct your
build system to compile them together with your project. Please look into the
<emphasis>Jamfile</emphasis> in <emphasis>boost_root</emphasis>/libs/thread/build
to find out which compiler options and defines you will need to get a clean compile.
Using the boost library in this way is the least recommended, and should only be
considered if avoiding dependency on &Boost.Build; is a requirement. Even if so
it might be a better option to use the library in it's precompiled form.
Precompiled downloads are available from the boost consulting web site, or as
part of most linux distributions.
</para>
</section>
</section>
<section id="thread.build.testing">
<title>Testing the &Boost.Thread; Libraries</title>
<para>
To test the &Boost.Thread; libraries using &Boost.Build;, simply change to the
directory <emphasis>boost_root</emphasis>/libs/thread/test and execute the command:
<programlisting>bjam --toolset=<emphasis>mytoolset</emphasis> test</programlisting>
</para>
</section>
</section>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, Boost.Threads, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, call_once</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">call_once</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Members">Members</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>call_once</code> routine and <code>once_flag</code> type can be used to
run a routine exactly once. This can be used to initialize data in a
<a href="definitions.html#Thread-safe">thread-safe</a> manner.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/once.hpp">&lt;boost/thread/once.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
typedef <i>[implementation defined]</i> once_flag;
const once_flag once_init = <i>[implementation defined]</i>;
void call_once(void (*func)(), once_flag&amp; flag);
} // namespace boost
</pre>
<h2><a name="Reference">Reference</a></h2>
<hr>
<h3>once_flag</h3>
<p>This implementation defined type is used as a flag to insure a routine is called only once.
Instances of this type should be statically initialized to <code>once_init</code>.</p>
<hr>
<h3>once_init</h3>
<p>This is a constant value used to initialize <code>once_flag</code> instances
to indicate that the logically associated routine has not been run yet.</p>
<hr>
<h3>call_once</h3>
<pre>
void call_once(void (*func)(), once_flag&amp; flag);
</pre>
<p><b>Requires:</b> The function <code>func</code> shall not throw exceptions.</p>
<p><b>Effects:</b> As if (in an atomic fashion)</p>
<code>
&nbsp;&nbsp;&nbsp;if (flag == once_init)<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;func();
</code>
<p><b>Postcondition:</b> <code>flag</code> != <code>once_init</code></p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/once.hpp&gt;</a>
#include &lt;cassert&gt;
int value=0;
boost::once_flag once = boost::once_init;
void init()
{
++value;
}
void thread_proc()
{
boost::call_once(&amp;init, once);
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i&lt;5; ++i)
threads.create_thread(&amp;thread_proc);
threads.join_all();
assert(value == 1);
}
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:changes Changes since boost 1.35]
The 1.36.0 release of Boost includes a few new features in the thread library:
* New generic __lock_multiple_ref__ and __try_lock_multiple_ref__ functions for locking multiple mutexes at once.
* Rvalue reference support for move semantics where the compilers supports it.
* A few bugs fixed and missing functions added (including the serious win32 condition variable bug).
* `scoped_try_lock` types are now backwards-compatible with Boost 1.34.0 and previous releases.
* Support for passing function arguments to the thread function by supplying additional arguments to the __thread__ constructor.
* Backwards-compatibility overloads added for `timed_lock` and `timed_wait` functions to allow use of `xtime` for timeouts.
[heading Changes since boost 1.34]
Almost every line of code in __boost_thread__ has been changed since the 1.34 release of boost. However, most of the interface
changes have been extensions, so the new code is largely backwards-compatible with the old code. The new features and breaking
changes are described below.
[heading New Features]
* Instances of __thread__ and of the various lock types are now movable.
* Threads can be interrupted at __interruption_points__.
* Condition variables can now be used with any type that implements the __lockable_concept__, through the use of
`boost::condition_variable_any` (`boost::condition` is a `typedef` to `boost::condition_variable_any`, provided for backwards
compatibility). `boost::condition_variable` is provided as an optimization, and will only work with
`boost::unique_lock<boost::mutex>` (`boost::mutex::scoped_lock`).
* Thread IDs are separated from __thread__, so a thread can obtain it's own ID (using `boost::this_thread::get_id()`), and IDs can
be used as keys in associative containers, as they have the full set of comparison operators.
* Timeouts are now implemented using the Boost DateTime library, through a typedef `boost::system_time` for absolute timeouts, and
with support for relative timeouts in many cases. `boost::xtime` is supported for backwards compatibility only.
* Locks are implemented as publicly accessible templates `boost::lock_guard`, `boost::unique_lock`, `boost::shared_lock`, and
`boost::upgrade_lock`, which are templated on the type of the mutex. The __lockable_concept__ has been extended to include publicly
available __lock_ref__ and __unlock_ref__ member functions, which are used by the lock types.
[heading Breaking Changes]
The list below should cover all changes to the public interface which break backwards compatibility.
* __try_mutex__ has been removed, and the functionality subsumed into __mutex__. __try_mutex__ is left as a `typedef`,
but is no longer a separate class.
* __recursive_try_mutex__ has been removed, and the functionality subsumed into
__recursive_mutex__. __recursive_try_mutex__ is left as a `typedef`, but is no longer a separate class.
* `boost::detail::thread::lock_ops` has been removed. Code that relies on the `lock_ops` implementation detail will no longer work,
as this has been removed, as it is no longer necessary now that mutex types now have public __lock_ref__ and __unlock_ref__ member
functions.
* `scoped_lock` constructors with a second parameter of type `bool` are no longer provided. With previous boost releases,
``boost::mutex::scoped_lock some_lock(some_mutex,false);`` could be used to create a lock object that was associated with a mutex,
but did not lock it on construction. This facility has now been replaced with the constructor that takes a
`boost::defer_lock_type` as the second parameter: ``boost::mutex::scoped_lock some_lock(some_mutex,boost::defer_lock);``
* The `locked()` member function of the `scoped_lock` types has been renamed to __owns_lock_ref__.
* You can no longer obtain a __thread__ instance representing the current thread: a default-constructed __thread__ object is not
associated with any thread. The only use for such a thread object was to support the comparison operators: this functionality has
been moved to __thread_id__.
* The broken `boost::read_write_mutex` has been replaced with __shared_mutex__.
* __mutex__ is now never recursive. For Boost releases prior to 1.35 __mutex__ was recursive on Windows and not on POSIX platforms.
* When using a __recursive_mutex__ with a call to [cond_any_wait_link `boost::condition_variable_any::wait()`], the mutex is only
unlocked one level, and not completely. This prior behaviour was not guaranteed and did not feature in the tests.
[endsect]

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/condition.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="condition">
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<purpose>
<para>An object of class <classname>condition</classname> is a
synchronization primitive used to cause a thread to wait until a
particular shared-data condition (or time) is met.</para>
</purpose>
<description>
<para>A <classname>condition</classname> object is always used in
conjunction with a <link linkend="thread.concepts.mutexes">mutex</link>
object (an object whose type is a model of a <link
linkend="thread.concepts.Mutex">Mutex</link> or one of its
refinements). The mutex object must be locked prior to waiting on the
condition, which is verified by passing a lock object (an object whose
type is a model of <link linkend="thread.concepts.Lock">Lock</link> or
one of its refinements) to the <classname>condition</classname> object's
wait functions. Upon blocking on the <classname>condition</classname>
object, the thread unlocks the mutex object. When the thread returns
from a call to one of the <classname>condition</classname> object's wait
functions the mutex object is again locked. The tricky unlock/lock
sequence is performed automatically by the
<classname>condition</classname> object's wait functions.</para>
<para>The <classname>condition</classname> type is often used to
implement the Monitor Object and other important patterns (see
&cite.SchmidtStalRohnertBuschmann; and &cite.Hoare74;). Monitors are one
of the most important patterns for creating reliable multithreaded
programs.</para>
<para>See <xref linkend="thread.glossary"/> for definitions of <link
linkend="thread.glossary.thread-state">thread states</link>
blocked and ready. Note that "waiting" is a synonym for blocked.</para>
</description>
<constructor>
<effects><simpara>Constructs a <classname>condition</classname>
object.</simpara></effects>
</constructor>
<destructor>
<effects><simpara>Destroys <code>*this</code>.</simpara></effects>
</destructor>
<method-group name="notification">
<method name="notify_one">
<type>void</type>
<effects><simpara>If there is a thread waiting on <code>*this</code>,
change that thread's state to ready. Otherwise there is no
effect.</simpara></effects>
<notes><simpara>If more than one thread is waiting on <code>*this</code>,
it is unspecified which is made ready. After returning to a ready
state the notified thread must still acquire the mutex again (which
occurs within the call to one of the <classname>condition</classname>
object's wait functions.)</simpara></notes>
</method>
<method name="notify_all">
<type>void</type>
<effects><simpara>Change the state of all threads waiting on
<code>*this</code> to ready. If there are no waiting threads,
<code>notify_all()</code> has no effect.</simpara></effects>
</method>
</method-group>
<method-group name="waiting">
<method name="wait">
<template>
<template-type-parameter name="ScopedLock"/>
</template>
<type>void</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="thread.concepts.ScopedLock">ScopedLock</link>
requirements.</simpara></requires>
<effects><simpara>Releases the lock on the <link
linkend="thread.concepts.mutexes">mutex object</link>
associated with <code>lock</code>, blocks the current thread of execution
until readied by a call to <code>this->notify_one()</code>
or<code> this->notify_all()</code>, and then reacquires the
lock.</simpara></effects>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
<method name="wait">
<template>
<template-type-parameter name="ScopedLock"/>
<template-type-parameter name="Pred"/>
</template>
<type>void</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<parameter name="pred">
<paramtype>Pred</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="thread.concepts.ScopedLock">ScopedLock</link>
requirements and the return from <code>pred()</code> is
convertible to <code>bool</code>.</simpara></requires>
<effects><simpara>As if: <code>while (!pred())
wait(lock)</code></simpara></effects>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
<method name="timed_wait">
<template>
<template-type-parameter name="ScopedLock"/>
</template>
<type>bool</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<parameter name="xt">
<paramtype>const <classname>boost::xtime</classname>&amp;</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="thread.concepts.ScopedLock">ScopedLock</link>
requirements.</simpara></requires>
<effects><simpara>Releases the lock on the <link
linkend="thread.concepts.mutexes">mutex object</link>
associated with <code>lock</code>, blocks the current thread of execution
until readied by a call to <code>this->notify_one()</code>
or<code> this->notify_all()</code>, or until time <code>xt</code>
is reached, and then reacquires the lock.</simpara></effects>
<returns><simpara><code>false</code> if time <code>xt</code> is reached,
otherwise <code>true</code>.</simpara></returns>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
<method name="timed_wait">
<template>
<template-type-parameter name="ScopedLock"/>
<template-type-parameter name="Pred"/>
</template>
<type>bool</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<parameter name="xt">
<paramtype>const <classname>boost::xtime</classname>&amp;</paramtype>
</parameter>
<parameter name="pred">
<paramtype>Pred</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="thread.concepts.ScopedLock">ScopedLock</link>
requirements and the return from <code>pred()</code> is
convertible to <code>bool</code>.</simpara></requires>
<effects><simpara>As if: <code>while (!pred()) { if (!timed_wait(lock,
xt)) return false; } return true;</code></simpara></effects>
<returns><simpara><code>false</code> if <code>xt</code> is reached,
otherwise <code>true</code>.</simpara></returns>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
</method-group>
</class>
</namespace>
</header>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, condition</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080" text="#000000">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">condition</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</a><br>
<A href="#Header">Header</a><br>
<A href="#Synopsis">Synopsis</a><br>
<A href="#Members">Members</a><br>
<A href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>An object of class <code>condition</code> is a synchronization primitive used to
cause a thread to wait until a particular shared-data condition (or time) is met.
A <code>condition</code> object is always used in conjunction with a mutex
object modeling a <a href="mutex_concept.html">Mutex Concept</a>. The mutex must be locked prior to waiting on the
<code>condition</code>, which is ensured by passing a lock object modeling a <a href="lock_concept.html">Lock
Concept</a> to the <code>condition</code> object's <code>wait</code> functions. While the thread is waiting on the <code>condition</code>
object,
the mutex associated with the lock is unlocked. When the thread returns
from a call to one of the <code>condition</code> object's <code>wait</code> functions,
the mutex is again locked. The tricky lock/unlock/lock sequence is performed
automatically by the <code>condition</code> object's <code>wait</code>
functions.</p>
<p>The <code>condition</code> type is often used to implement the <i>Monitor Object</i>
and other important patterns. See <A href="bibliography.html#Schmidt-00">[Schmidt-00]</a>
and <A href="bibliography.html#Hoare-74">[Hoare 74]</a>. Monitors are one of the most
important patterns for creating reliable multithreaded programs.</p>
<p>See <A href="definitions.html">Formal Definitions</a> for definitions of thread
states <A href="definitions.html#state">blocked</a> and
<A href="definitions.html#state">ready</a>. Note that "waiting" is a synonym
for blocked.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <A href="../../../boost/thread/condition.hpp">&lt;boost/thread/condition.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
class condition : private <A href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class condition meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
condition();
~condition();
void notify_one();
void notify_all();
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>&gt;
void wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock);
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>, typename <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A>&gt;
void wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock, <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A> pred);
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>&gt;
bool timed_wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock, const xtime&amp; xt);
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>, typename <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A>&gt;
bool timed_wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock, const xtime&amp; xt, <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A> pred);
};
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
condition();
</pre>
<p><b>Effects:</b> Constructs a <code>condition</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~condition();
</pre>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<hr>
<h3>notify_one</h3>
<pre>
void notify_one();
</pre>
<p><b>Effects:</b> If there is a thread waiting on <code>*this</code>, change
that thread's state to ready. Otherwise there is no effect.</p>
<p><b>Notes:</b> If more that one thread is waiting on the condition, it is
unspecified which is made ready.</p>
<hr>
<h3>notify_all</h3>
<pre>
void notify_all();
</pre>
<p><b>Effects:</b> Change the state of all threads waiting on <code>*this</code>
to ready. If there are no waiting threads, <code>notify_all()</code> has no effect.</p>
<hr>
<h3>wait</h3>
<pre>
template &lt;typename ScopedLock&gt;
void wait(ScopedLock&amp; lock);
</pre>
<p><b>Requires:</b> ScopedLock meets the
<A href="lock_concept.html#ScopedLock">ScopedLock</a> requirements.</p>
<p><b>Effects:</b> Releases the lock on the <A href="mutex_concept.html">mutex model</a>
associated with <code>lock</code>, blocks the current thread of execution until readied
by a call to <code>this-&gt;notify_one()</code> or <code>this-&gt;notify_all()</code>,
and then reacquires the lock. All effects occur in an atomic fashion.</p>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code>
if <code>!lock.locked()</code></p>
<p><b>Danger:</b> This version should always be used within a loop checking that the
state logically associated with the <code>condition</code> has become true. Without
the loop, race conditions can ensue due to possible "spurious wake ups". The second
version encapsulates this loop idiom internally and is generally the preferred method.</p>
<pre>
template &lt;typename ScopedLock, typename Pr&gt;
void wait(ScopedLock&amp; lock, Pr pred);
</pre>
<p><b>Requires:</b> ScopedLock meets the
<A href="lock_concept.html#ScopedLock">ScopedLock</a> requirements, return from
<code>pred()</code> convertible to bool.</p>
<p><b>Effects:</b> As if:</p>
<code>
&nbsp;&nbsp;&nbsp;while (!pred()) wait(lock)
</code>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code> if
<code>!lock.locked()</code></p>
<hr>
<h3>timed_wait</h3>
<pre>
template &lt;typename ScopedTimedLock&gt;
bool timed_wait(ScopedTimedLock&amp; lock, const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Requires:</b> ScopedTimeLock meets the
<A href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a> requirements.</p>
<p><b>Effects:</b> Releases the lock on the <A href="mutex_concept.html">mutex model</a>
associated with the <code>lock</code>, blocks the current thread of execution until
readied by a call to <code>this-&gt;notify_one()</code> or
<code>this-&gt;notify_all()</code>, or until <code>xt</code>, and then reacquires the
lock. All effects occur in an atomic fashion.</p>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code> if
<code>!lock.locked()</code></p>
<p><b>Danger:</b> This version should always be used within a loop checking that the
state logically associated with the <code>condition</code> has become true. Without
the loop, race conditions can ensue due to "spurious wake ups". The second version
encapsulates this loop idiom internally and is generally the preferred method.</p>
<p><b>Returns:</b> <code>false</code> if <code>xt</code> is reached, otherwise
<code>true</code>.</p>
<pre>
template &lt;typename ScopedTimedLock, typename Pr&gt;
bool timed_wait(ScopedTimedLock&amp; lock, const <a href="xtime.html">xtime</a>&amp; xt, Pr pred);
</pre>
<p><b>Requires: </b>ScopedTimeLock meets the
<A href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a> requirements,
return from <code>pred()</code> convertible to bool.</p>
<p><b>Effects: </b>As if:</p>
<code>
&nbsp;&nbsp;&nbsp;while (!pred())<br>
&nbsp;&nbsp;&nbsp;{<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (!timed_wait(lock, xt))<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return false;<br>
&nbsp;&nbsp;&nbsp;}
</code>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code> if
<code>!lock.locked()</code></p>
<p><b>Returns:</b> <code>false</code> if <code>xt</code> is reached, otherwise
<code>true</code>.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include &lt;iostream&gt;
#include &lt;vector&gt;
#include <A href="../../../boost/utility.hpp">&lt;boost/utility.hpp&gt;</a>
#include <A href="../../../boost/thread/condition.hpp">&lt;boost/thread/condition.hpp&gt;</a>
#include <A href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
class bounded_buffer : private boost::noncopyable
{
public:
typedef boost::mutex::scoped_lock lock;
bounded_buffer(int n) : begin(0), end(0), buffered(0), circular_buf(n) { }
void send (int m) {
lock lk(monitor);
while (buffered == circular_buf.size())
buffer_not_full.wait(lk);
circular_buf[end] = m;
end = (end+1) % circular_buf.size();
++buffered;
buffer_not_empty.notify_one();
}
int receive() {
lock lk(monitor);
while (buffered == 0)
buffer_not_empty.wait(lk);
int i = circular_buf[begin];
begin = (begin+1) % circular_buf.size();
--buffered;
buffer_not_full.notify_one();
return i;
}
private:
int begin, end, buffered;
std::vector&lt;int&gt; circular_buf;
boost::condition buffer_not_full, buffer_not_empty;
boost::mutex monitor;
};
bounded_buffer buf(2);
void sender() {
int n = 0;
while (n &lt; 100) {
buf.send(n);
std::cout &lt;&lt; &quot;sent: &quot; &lt;&lt; n &lt;&lt; std::endl;
++n;
}
buf.send(-1);
}
void receiver() {
int n;
do {
n = buf.receive();
std::cout &lt;&lt; &quot;received: &quot; &lt;&lt; n &lt;&lt; std::endl;
} while (n != -1); // -1 indicates end of buffer
}
int main(int, char*[])
{
boost::thread thrd1(&amp;sender);
boost::thread thrd2(&amp;receiver);
thrd1.join();
thrd2.join();
return 0;
}
</pre>
<p>Typical output (dependent on scheduling policies) is:</p>
<pre>
sent: 0
sent: 1
received: 0
received: 1
sent: 2
sent: 3
received: 2
received: 3
sent: 4
received: 4
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -1,513 +0,0 @@
[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:condvar_ref Condition Variables]
[heading Synopsis]
The classes `condition_variable` and `condition_variable_any` provide a
mechanism for one thread to wait for notification from another thread that a
particular condition has become true. The general usage pattern is that one
thread locks a mutex and then calls `wait` on an instance of
`condition_variable` or `condition_variable_any`. When the thread is woken from
the wait, then it checks to see if the appropriate condition is now true, and
continues if so. If the condition is not true, then the thread then calls `wait`
again to resume waiting. In the simplest case, this condition is just a boolean
variable:
boost::condition_variable cond;
boost::mutex mut;
bool data_ready;
void process_data();
void wait_for_data_to_process()
{
boost::unique_lock<boost::mutex> lock(mut);
while(!data_ready)
{
cond.wait(lock);
}
process_data();
}
Notice that the `lock` is passed to `wait`: `wait` will atomically add the
thread to the set of threads waiting on the condition variable, and unlock the
mutex. When the thread is woken, the mutex will be locked again before the call
to `wait` returns. This allows other threads to acquire the mutex in order to
update the shared data, and ensures that the data associated with the condition
is correctly synchronized.
In the mean time, another thread sets the condition to `true`, and then calls
either `notify_one` or `notify_all` on the condition variable to wake one
waiting thread or all the waiting threads respectively.
void retrieve_data();
void prepare_data();
void prepare_data_for_processing()
{
retrieve_data();
prepare_data();
{
boost::lock_guard<boost::mutex> lock(mut);
data_ready=true;
}
cond.notify_one();
}
Note that the same mutex is locked before the shared data is updated, but that
the mutex does not have to be locked across the call to `notify_one`.
This example uses an object of type `condition_variable`, but would work just as
well with an object of type `condition_variable_any`: `condition_variable_any`
is more general, and will work with any kind of lock or mutex, whereas
`condition_variable` requires that the lock passed to `wait` is an instance of
`boost::unique_lock<boost::mutex>`. This enables `condition_variable` to make
optimizations in some cases, based on the knowledge of the mutex type;
`condition_variable_any` typically has a more complex implementation than
`condition_variable`.
[section:condition_variable Class `condition_variable`]
#include <boost/thread/condition_variable.hpp>
namespace boost
{
class condition_variable
{
public:
condition_variable();
~condition_variable();
void notify_one();
void notify_all();
void wait(boost::unique_lock<boost::mutex>& lock);
template<typename predicate_type>
void wait(boost::unique_lock<boost::mutex>& lock,predicate_type predicate);
bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::system_time const& abs_time);
template<typename duration_type>
bool timed_wait(boost::unique_lock<boost::mutex>& lock,duration_type const& rel_time);
template<typename predicate_type>
bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::system_time const& abs_time,predicate_type predicate);
template<typename duration_type,typename predicate_type>
bool timed_wait(boost::unique_lock<boost::mutex>& lock,duration_type const& rel_time,predicate_type predicate);
// backwards compatibility
bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::xtime const& abs_time);
template<typename predicate_type>
bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::xtime const& abs_time,predicate_type predicate);
};
}
[section:constructor `condition_variable()`]
[variablelist
[[Effects:] [Constructs an object of class `condition_variable`.]]
[[Throws:] [__thread_resource_error__ if an error occurs.]]
]
[endsect]
[section:destructor `~condition_variable()`]
[variablelist
[[Precondition:] [All threads waiting on `*this` have been notified by a call to
`notify_one` or `notify_all` (though the respective calls to `wait` or
`timed_wait` need not have returned).]]
[[Effects:] [Destroys the object.]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:notify_one `void notify_one()`]
[variablelist
[[Effects:] [If any threads are currently __blocked__ waiting on `*this` in a call
to `wait` or `timed_wait`, unblocks one of those threads.]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:notify_all `void notify_all()`]
[variablelist
[[Effects:] [If any threads are currently __blocked__ waiting on `*this` in a call
to `wait` or `timed_wait`, unblocks all of those threads.]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:wait `void wait(boost::unique_lock<boost::mutex>& lock)`]
[variablelist
[[Precondition:] [`lock` is locked by the current thread, and either no other
thread is currently waiting on `*this`, or the execution of the `mutex()` member
function on the `lock` objects supplied in the calls to `wait` or `timed_wait`
in all the threads currently waiting on `*this` would return the same value as
`lock->mutex()` for this call to `wait`.]]
[[Effects:] [Atomically call `lock.unlock()` and blocks the current thread. The
thread will unblock when notified by a call to `this->notify_one()` or
`this->notify_all()`, or spuriously. When the thread is unblocked (for whatever
reason), the lock is reacquired by invoking `lock.lock()` before the call to
`wait` returns. The lock is also reacquired by invoking `lock.lock()` if the
function exits with an exception.]]
[[Postcondition:] [`lock` is locked by the current thread.]]
[[Throws:] [__thread_resource_error__ if an error
occurs. __thread_interrupted__ if the wait was interrupted by a call to
__interrupt__ on the __thread__ object associated with the current thread of execution.]]
]
[endsect]
[section:wait_predicate `template<typename predicate_type> void wait(boost::unique_lock<boost::mutex>& lock, predicate_type pred)`]
[variablelist
[[Effects:] [As-if ``
while(!pred())
{
wait(lock);
}
``]]
]
[endsect]
[section:timed_wait `bool timed_wait(boost::unique_lock<boost::mutex>& lock,boost::system_time const& abs_time)`]
[variablelist
[[Precondition:] [`lock` is locked by the current thread, and either no other
thread is currently waiting on `*this`, or the execution of the `mutex()` member
function on the `lock` objects supplied in the calls to `wait` or `timed_wait`
in all the threads currently waiting on `*this` would return the same value as
`lock->mutex()` for this call to `wait`.]]
[[Effects:] [Atomically call `lock.unlock()` and blocks the current thread. The
thread will unblock when notified by a call to `this->notify_one()` or
`this->notify_all()`, when the time as reported by `boost::get_system_time()`
would be equal to or later than the specified `abs_time`, or spuriously. When
the thread is unblocked (for whatever reason), the lock is reacquired by
invoking `lock.lock()` before the call to `wait` returns. The lock is also
reacquired by invoking `lock.lock()` if the function exits with an exception.]]
[[Returns:] [`false` if the call is returning because the time specified by
`abs_time` was reached, `true` otherwise.]]
[[Postcondition:] [`lock` is locked by the current thread.]]
[[Throws:] [__thread_resource_error__ if an error
occurs. __thread_interrupted__ if the wait was interrupted by a call to
__interrupt__ on the __thread__ object associated with the current thread of execution.]]
]
[endsect]
[section:timed_wait_rel `template<typename duration_type> bool timed_wait(boost::unique_lock<boost::mutex>& lock,duration_type const& rel_time)`]
[variablelist
[[Precondition:] [`lock` is locked by the current thread, and either no other
thread is currently waiting on `*this`, or the execution of the `mutex()` member
function on the `lock` objects supplied in the calls to `wait` or `timed_wait`
in all the threads currently waiting on `*this` would return the same value as
`lock->mutex()` for this call to `wait`.]]
[[Effects:] [Atomically call `lock.unlock()` and blocks the current thread. The
thread will unblock when notified by a call to `this->notify_one()` or
`this->notify_all()`, after the period of time indicated by the `rel_time`
argument has elapsed, or spuriously. When the thread is unblocked (for whatever
reason), the lock is reacquired by invoking `lock.lock()` before the call to
`wait` returns. The lock is also reacquired by invoking `lock.lock()` if the
function exits with an exception.]]
[[Returns:] [`false` if the call is returning because the time period specified
by `rel_time` has elapsed, `true` otherwise.]]
[[Postcondition:] [`lock` is locked by the current thread.]]
[[Throws:] [__thread_resource_error__ if an error
occurs. __thread_interrupted__ if the wait was interrupted by a call to
__interrupt__ on the __thread__ object associated with the current thread of execution.]]
]
[note The duration overload of timed_wait is difficult to use correctly. The overload taking a predicate should be preferred in most cases.]
[endsect]
[section:timed_wait_predicate `template<typename predicate_type> bool timed_wait(boost::unique_lock<boost::mutex>& lock, boost::system_time const& abs_time, predicate_type pred)`]
[variablelist
[[Effects:] [As-if ``
while(!pred())
{
if(!timed_wait(lock,abs_time))
{
return pred();
}
}
return true;
``]]
]
[endsect]
[endsect]
[section:condition_variable_any Class `condition_variable_any`]
#include <boost/thread/condition_variable.hpp>
namespace boost
{
class condition_variable_any
{
public:
condition_variable_any();
~condition_variable_any();
void notify_one();
void notify_all();
template<typename lock_type>
void wait(lock_type& lock);
template<typename lock_type,typename predicate_type>
void wait(lock_type& lock,predicate_type predicate);
template<typename lock_type>
bool timed_wait(lock_type& lock,boost::system_time const& abs_time);
template<typename lock_type,typename duration_type>
bool timed_wait(lock_type& lock,duration_type const& rel_time);
template<typename lock_type,typename predicate_type>
bool timed_wait(lock_type& lock,boost::system_time const& abs_time,predicate_type predicate);
template<typename lock_type,typename duration_type,typename predicate_type>
bool timed_wait(lock_type& lock,duration_type const& rel_time,predicate_type predicate);
// backwards compatibility
template<typename lock_type>
bool timed_wait(lock_type>& lock,boost::xtime const& abs_time);
template<typename lock_type,typename predicate_type>
bool timed_wait(lock_type& lock,boost::xtime const& abs_time,predicate_type predicate);
};
}
[section:constructor `condition_variable_any()`]
[variablelist
[[Effects:] [Constructs an object of class `condition_variable_any`.]]
[[Throws:] [__thread_resource_error__ if an error occurs.]]
]
[endsect]
[section:destructor `~condition_variable_any()`]
[variablelist
[[Precondition:] [All threads waiting on `*this` have been notified by a call to
`notify_one` or `notify_all` (though the respective calls to `wait` or
`timed_wait` need not have returned).]]
[[Effects:] [Destroys the object.]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:notify_one `void notify_one()`]
[variablelist
[[Effects:] [If any threads are currently __blocked__ waiting on `*this` in a call
to `wait` or `timed_wait`, unblocks one of those threads.]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:notify_all `void notify_all()`]
[variablelist
[[Effects:] [If any threads are currently __blocked__ waiting on `*this` in a call
to `wait` or `timed_wait`, unblocks all of those threads.]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:wait `template<typename lock_type> void wait(lock_type& lock)`]
[variablelist
[[Effects:] [Atomically call `lock.unlock()` and blocks the current thread. The
thread will unblock when notified by a call to `this->notify_one()` or
`this->notify_all()`, or spuriously. When the thread is unblocked (for whatever
reason), the lock is reacquired by invoking `lock.lock()` before the call to
`wait` returns. The lock is also reacquired by invoking `lock.lock()` if the
function exits with an exception.]]
[[Postcondition:] [`lock` is locked by the current thread.]]
[[Throws:] [__thread_resource_error__ if an error
occurs. __thread_interrupted__ if the wait was interrupted by a call to
__interrupt__ on the __thread__ object associated with the current thread of execution.]]
]
[endsect]
[section:wait_predicate `template<typename lock_type,typename predicate_type> void wait(lock_type& lock, predicate_type pred)`]
[variablelist
[[Effects:] [As-if ``
while(!pred())
{
wait(lock);
}
``]]
]
[endsect]
[section:timed_wait `template<typename lock_type> bool timed_wait(lock_type& lock,boost::system_time const& abs_time)`]
[variablelist
[[Effects:] [Atomically call `lock.unlock()` and blocks the current thread. The
thread will unblock when notified by a call to `this->notify_one()` or
`this->notify_all()`, when the time as reported by `boost::get_system_time()`
would be equal to or later than the specified `abs_time`, or spuriously. When
the thread is unblocked (for whatever reason), the lock is reacquired by
invoking `lock.lock()` before the call to `wait` returns. The lock is also
reacquired by invoking `lock.lock()` if the function exits with an exception.]]
[[Returns:] [`false` if the call is returning because the time specified by
`abs_time` was reached, `true` otherwise.]]
[[Postcondition:] [`lock` is locked by the current thread.]]
[[Throws:] [__thread_resource_error__ if an error
occurs. __thread_interrupted__ if the wait was interrupted by a call to
__interrupt__ on the __thread__ object associated with the current thread of execution.]]
]
[endsect]
[section:timed_wait_rel `template<typename lock_type,typename duration_type> bool timed_wait(lock_type& lock,duration_type const& rel_time)`]
[variablelist
[[Effects:] [Atomically call `lock.unlock()` and blocks the current thread. The
thread will unblock when notified by a call to `this->notify_one()` or
`this->notify_all()`, after the period of time indicated by the `rel_time`
argument has elapsed, or spuriously. When the thread is unblocked (for whatever
reason), the lock is reacquired by invoking `lock.lock()` before the call to
`wait` returns. The lock is also reacquired by invoking `lock.lock()` if the
function exits with an exception.]]
[[Returns:] [`false` if the call is returning because the time period specified
by `rel_time` has elapsed, `true` otherwise.]]
[[Postcondition:] [`lock` is locked by the current thread.]]
[[Throws:] [__thread_resource_error__ if an error
occurs. __thread_interrupted__ if the wait was interrupted by a call to
__interrupt__ on the __thread__ object associated with the current thread of execution.]]
]
[note The duration overload of timed_wait is difficult to use correctly. The overload taking a predicate should be preferred in most cases.]
[endsect]
[section:timed_wait_predicate `template<typename lock_type,typename predicate_type> bool timed_wait(lock_type& lock, boost::system_time const& abs_time, predicate_type pred)`]
[variablelist
[[Effects:] [As-if ``
while(!pred())
{
if(!timed_wait(lock,abs_time))
{
return pred();
}
}
return true;
``]]
]
[endsect]
[endsect]
[section:condition Typedef `condition`]
#include <boost/thread/condition.hpp>
typedef condition_variable_any condition;
The typedef `condition` is provided for backwards compatibility with previous boost releases.
[endsect]
[endsect]

103
doc/config.html Normal file
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, Configuration Information</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Configuration Information</h2>
</td>
</tr>
</table>
<hr>
<p><b>Boost.Threads</b> uses several configuration macros in <a href="../../config/config.htm"> &lt;boost/config.hpp&gt;</a>.
These macros are documented here. Most of the macros are
of interest only to developers attempting to provide new implementations of <b>Boost.Threads</b>.
The one exception to this is BOOST_HAS_THREADS.</p>
<table cellspacing="10" width="100%">
<tr>
<td valign="top">
<b>Macro</b>
</td>
<td valign="top">
<b>Meaning</b>
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_THREADS
</td>
<td valign="top">
Indicates that threading support is available. This means both that there is a
platform specific implementation for <b>Boost.Threads</b> and that threading
support has been enabled in a platform specific manner. For instance, on the
Win32 platform there's an implementation for <b>Boost.Threads</b> but unless
the program is compiled against one of the multi-threading runtimes
(often determined by the
compiler predefining the macro _MT) the
BOOST_HAS_THREADS macro remains undefined.
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_WINTHREADS
</td>
<td valign="top">
Indicates that the platform has the Microsoft Win32 threading libraries,
and that they should be used
to implement <b>Boost.Threads</b>.
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_PTHREADS
</td>
<td valign="top">
Indicates that the platform has the POSIX pthreads libraries, and that
they should be used
to implement <b>Boost.Threads</b>.
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_FTIME
</td>
<td valign="top">
Indicates that the implementation should use GetSystemTimeAsFileTime() and
the FILETIME type to calculate the current time. This is an implementation
detail used by boost::detail::getcurtime().
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_GETTTIMEOFDAY
</td>
<td valign="top">
Indicates that the implementation should use gettimeofday() to calculate the
current time. This is an implementation detail used by boost::detail::getcurtime().
</td>
</tr>
</table>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->18 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39344" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.configuration" last-revision="$Date$">
<title>Configuration</title>
<para>&Boost.Thread; uses several configuration macros in &lt;boost/config.hpp&gt;,
as well as configuration macros meant to be supplied by the application. These
macros are documented here.
</para>
<section id="thread.configuration.public">
<title>Library Defined Public Macros</title>
<para>
These macros are defined by &Boost.Thread; but are expected to be used
by application code.
</para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>Macro</entry>
<entry>Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry>BOOST_HAS_THREADS</entry>
<entry>
Indicates that threading support is available. This means both that there
is a platform specific implementation for &Boost.Thread; and that
threading support has been enabled in a platform specific manner. For instance,
on the Win32 platform there&#39;s an implementation for &Boost.Thread;
but unless the program is compiled against one of the multithreading runtimes
(often determined by the compiler predefining the macro _MT) the BOOST_HAS_THREADS
macro remains undefined.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</section>
<section id="thread.configuration.implementation">
<title>Library Defined Implementation Macros</title>
<para>
These macros are defined by &Boost.Thread; and are implementation details
of interest only to implementors.
</para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>Macro</entry>
<entry>Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry>BOOST_HAS_WINTHREADS</entry>
<entry>
Indicates that the platform has the Microsoft Win32 threading libraries,
and that they should be used to implement &Boost.Thread;.
</entry>
</row>
<row>
<entry>BOOST_HAS_PTHREADS</entry>
<entry>
Indicates that the platform has the POSIX pthreads libraries, and that
they should be used to implement &Boost.Thread;.
</entry>
</row>
<row>
<entry>BOOST_HAS_FTIME</entry>
<entry>
Indicates that the implementation should use GetSystemTimeAsFileTime()
and the FILETIME type to calculate the current time. This is an implementation
detail used by boost::detail::getcurtime().
</entry>
</row>
<row>
<entry>BOOST_HAS_GETTTIMEOFDAY</entry>
<entry>
Indicates that the implementation should use gettimeofday() to calculate
the current time. This is an implementation detail used by boost::detail::getcurtime().
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</section>
</section>

244
doc/definitions.html Normal file
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<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost.Threads Definitions</title>
</head>
<body bgcolor="#FFFFFF">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center"> Definitions</h2>
</td>
</tr>
</table>
<h2>Introduction</h2>
<p>The definitions are given in terms of the <a href="bibliography.html#ISO-98"> C++ Standard</a>.&nbsp; References to the standard
are in the form [1.2.3/4], which
represents the section number, with the paragraph number following the &quot;/&quot;.</p>
<p>Because the definitions are written in something akin to
&quot;standardese&quot;, they can be difficult to understand.&nbsp; The intent
isn't to confuse, but rather to clarify the additional requirements
Boost.Threads places on a C++ implementation as defined by the C++ Standard.</p>
<h2>Definitions</h2>
<h3>Thread</h3>
<p>Thread is short for &quot;thread of execution&quot;. A thread of execution is an execution environment [1.9/7] within the execution environment
of a C++ program [1.9]. The main() function [3.6.1] of the program is the
initial function of the initial thread. A program in a multi-threading
environment always has an initial thread even if the program explicitly creates
no additional threads.</p>
<p>Unless otherwise specified, each thread shares all aspects of its execution environment with
other threads in the program. Shared aspects of the execution environment
include, but are not limited to, the following:</p>
<ul>
<li>Static storage duration (static, extern) objects [3.7.1].</li>
</ul>
<ul>
<li>Dynamic storage duration (heap) objects [3.7.3].&nbsp; Thus each memory
allocation will return a unique addresses, regardless of the thread making
the allocation request.</li>
</ul>
<ul>
<li>Automatic storage duration (stack) objects [3.7.2] accessed via pointer or
reference from another thread.</li>
</ul>
<ul>
<li>Resources provided by the operating
system.&nbsp; For example, files.</li>
</ul>
<ul>
<li>The program itself.&nbsp; In other words, each thread is executing some
function of the same program, not a totally different program.</li>
</ul>
<p>Each thread has its own:</p>
<ul>
<li>Registers and current execution sequence (program counter) [1.9/5].</li>
</ul>
<ul>
<li>Automatic storage duration (stack) objects [3.7.2].</li>
</ul>
<h3><a name="Thread-safe">Thread-safe</a></h3>
<p>A program is thread-safe if it has no <a href="#Race condition">race
conditions</a>, does not <a href="#Deadlock">deadlock</a>, and has no <a href="#Priority failure">priority
failures</a>.</p>
<p>Note that thread-safety does not necessarily imply efficiency, and than while
some thread-safety violations can be determined statically at compile time, many
thread-safety errors can only only be detected at runtime.</p>
<h3>Thread <a name="State">State</a></h3>
<p>During the lifetime of a thread, it shall be in one of the following
states:</p>
<table border="1" cellpadding="5">
<tr>
<td><b>State</b></td>
<td><b>Description</b></td>
</tr>
<tr>
<td>Ready</td>
<td>Ready to run, but waiting for a processor.</td>
</tr>
<tr>
<td>Running</td>
<td>Currently executing on a processor. Zero or more threads may be running
at any time, with a maximum equal to the number of processors.&nbsp;</td>
</tr>
<tr>
<td>Blocked</td>
<td>Waiting for some resource other than a processor which is not currently
available, or for the completion of calls to library functions [1.9/6].
The term &quot;waiting&quot; is synonymous for &quot;blocked&quot;</td>
</tr>
<tr>
<td>Terminated</td>
<td>Finished execution but not yet detached or joined.</td>
</tr>
</table>
<p>Thread state transitions shall occur only as specified:</p>
<table border="1" cellpadding="5">
<tr>
<td><b>From</b></td>
<td><b>To</b></td>
<td><b>Cause</b></td>
</tr>
<tr>
<td>
<p align="left">[none]</td>
<td>Ready</td>
<td>Thread is created by a call to a library function.&nbsp; In the case of
the initial thread, creation is implicit and occurs during the startup of
the main() function [3.6.1].</td>
</tr>
<tr>
<td>Ready</td>
<td>Running</td>
<td>Processor becomes available.</td>
</tr>
<tr>
<td>Running</td>
<td>Ready</td>
<td>Thread preempted.</td>
</tr>
<tr>
<td>Running</td>
<td>Blocked</td>
<td>Thread calls a library function which waits for a resource or for the
completion of I/O.</td>
</tr>
<tr>
<td>Running</td>
<td>Terminated</td>
<td>Thread returns from its initial function, calls a thread termination
library function, or is cancelled by some other thread calling a thread
termination library function.</td>
</tr>
<tr>
<td>Blocked</td>
<td>Ready</td>
<td>The resource being waited for becomes available, or the blocking library
function completes.</td>
</tr>
<tr>
<td>Terminated</td>
<td>[none]</td>
<td>Thread is detached or joined by some other thread calling the
appropriate library function, or by program termination [3.6.3].</td>
</tr>
</table>
<p>[Note: if a suspend() function is added to the threading library, additional
transitions to the blocked state will have to be added to the above table.]</p>
<h3><a name="Race condition">Race condition</a></h3>
<p>A race condition is what occurs when multiple threads read and
write to the same memory without proper synchronization, resulting in an
incorrect value being read or written.&nbsp; The result of a race condition may
be a bit pattern which isn't even a valid value for the data type. A race
condition results in undefined behavior [1.3.12].</p>
<p>Race conditions can be prevented by serializing memory access
using the tools provided by Boost.Threads.&nbsp;</p>
<h3><a name="Deadlock">Deadlock</a></h3>
<p>Deadlock is an execution state where for some set of threads, each thread in
the set is blocked waiting for some action by one of the other threads in the
set. Since each is waiting on the others, none will ever become ready again.</p>
<h3><a name="Priority failure">Priority failure</a></h3>
<p>A priority failure (such as priority inversion or infinite overtaking) occurs
when threads executed in such a sequence that required work is not performed in
time to be useful.</p>
<h2>Memory visibility between threads</h2>
<p>An address [1.7] shall always point to the same memory byte, regardless of the
thread or processor dereferencing the address.</p>
<p>An object [1.8, 1.9] is accessible from multiple threads if it is of
static storage duration (static, extern) [3.7.1], or if a pointer or reference to
it is explicitly or
implicitly dereferenced in multiple threads.</p>
<p>For an object accessible from multiple threads, the value of the object
accessed from one thread may be indeterminate or different than the value
accessed from another thread, except under the conditions specified in the following
table.&nbsp;&nbsp; For the same row of the table, the value of an object
accessible at the indicated sequence point in thread A will be determinate and the
same if accessed at or after the indicated sequence point in thread B, provided
the object is not otherwise modified. In the table, the
&quot;sequence point at a call&quot; is the sequence point after the evaluation
of all function arguments [1.9/17], while the &quot;sequence point after a
call&quot; is the sequence point after the copying of the returned
value...&quot; [1.9/17].</p>
<table border="1" cellpadding="5">
<tr>
<td align="center"><b>Thread A</b></td>
<td align="center"><b>Thread B</b></td>
</tr>
<tr>
<td>The sequence point at a call to a library thread-creation
function.&nbsp;</td>
<td>The first sequence point of the initial function in the new thread
created by the Thread A call.</td>
</tr>
<tr>
<td>The sequence point at a call to a library function which locks a mutex,
directly or by waiting for a condition variable.</td>
<td>The sequence point after a call to a library function which unlocks the
same mutex.</td>
</tr>
<tr>
<td>The last sequence point before thread termination.</td>
<td>The sequence point after a call to a library function which joins the
terminated thread.</td>
</tr>
<tr>
<td>The sequence point at a call to a library function which signals or
broadcasts a condition variable.</td>
<td>The sequence point after the call to the library function which was
waiting on that same condition variable or signal.</td>
</tr>
</table>
<p>The architecture of the execution environment and the observable behavior of
the abstract machine [1.9] shall be the same on all processors.</p>
<p>The latitude granted by the C++ standard for an implementation to alter the
definition of observable behavior of the abstract machine to include additional library I/O
functions [1.9/6] is extended to include threading library functions.</p>
<p>When an exception is thrown and there is no matching exception handler in the
same thread, behavior is undefined.&nbsp; The preferred behavior is the same as when there is no matching exception handler
in a program [15.3/9].&nbsp; That is, terminate() is called, and it is implementation defined
whether or not the stack is unwound.</p>
<h2><a name="Acknowledgements">Acknowledgements</a></h2>
<p>This document has been much improved by the incorporation of comments from
William Kempf.</p>
<p>The visibility rules are based on <a href="bibliography.html#Butenhof-97">[Butenhof
97]</a>.&nbsp;</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %b %Y" startspan -->07 Aug 2001<!--webbot bot="Timestamp" endspan i-checksum="14762" -->
</p>
<p>© Copyright Beman Dawes, 2001</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
</body>
</html>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.design" last-revision="$Date$">
<title>Design</title>
<para>With client/server and three-tier architectures becoming common place
in today's world, it's becoming increasingly important for programs to be
able to handle parallel processing. Modern day operating systems usually
provide some support for this through native thread APIs. Unfortunately,
writing portable code that makes use of parallel processing in C++ is made
very difficult by a lack of a standard interface for these native APIs.
Further, these APIs are almost universally C APIs and fail to take
advantage of C++'s strengths, or to address concepts unique to C++, such as
exceptions.</para>
<para>The &Boost.Thread; library is an attempt to define a portable interface
for writing parallel processes in C++.</para>
<section id="thread.design.goals">
<title>Goals</title>
<para>The &Boost.Thread; library has several goals that should help to set
it apart from other solutions. These goals are listed in order of precedence
with full descriptions below.
<variablelist>
<varlistentry>
<term>Portability</term>
<listitem>
<para>&Boost.Thread; was designed to be highly portable. The goal is
for the interface to be easily implemented on any platform that
supports threads, and possibly even on platforms without native thread
support.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Safety</term>
<listitem>
<para>&Boost.Thread; was designed to be as safe as possible. Writing
<link linkend="thread.glossary.thread-safe">thread-safe</link>
code is very difficult and successful libraries must strive to
insulate the programmer from dangerous constructs as much as
possible. This is accomplished in several ways:
<itemizedlist>
<listitem>
<para>C++ language features are used to make correct usage easy
(if possible) and error-prone usage impossible or at least more
difficult. For example, see the <link
linkend="thread.concepts.Mutex">Mutex</link> and <link
linkend="thread.concepts.Lock">Lock</link> designs, and note
how they interact.</para>
</listitem>
<listitem>
<para>Certain traditional concurrent programming features are
considered so error-prone that they are not provided at all. For
example, see <xref linkend="thread.rationale.events" />.</para>
</listitem>
<listitem>
<para>Dangerous features, or features which may be misused, are
identified as such in the documentation to make users aware of
potential pitfalls.</para>
</listitem>
</itemizedlist></para>
</listitem>
</varlistentry>
<varlistentry>
<term>Flexibility</term>
<listitem>
<para>&Boost.Thread; was designed to be flexible. This goal is often
at odds with <emphasis>safety</emphasis>. When functionality might be
compromised by the desire to keep the interface safe, &Boost.Thread;
has been designed to provide the functionality, but to make it's use
prohibitive for general use. In other words, the interfaces have been
designed such that it's usually obvious when something is unsafe, and
the documentation is written to explain why.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Efficiency</term>
<listitem>
<para>&Boost.Thread; was designed to be as efficient as
possible. When building a library on top of another library there is
always a danger that the result will be so much slower than the
"native" API that programmers are inclined to ignore the higher level
API. &Boost.Thread; was designed to minimize the chances of this
occurring. The interfaces have been crafted to allow an implementation
the greatest chance of being as efficient as possible. This goal is
often at odds with the goal for <emphasis>safety</emphasis>. Every
effort was made to ensure efficient implementations, but when in
conflict <emphasis>safety</emphasis> has always taken
precedence.</para>
</listitem>
</varlistentry>
</variablelist></para>
</section>
<section>
<title>Iterative Phases</title>
<para>Another goal of &Boost.Thread; was to take a dynamic, iterative
approach in its development. The computing industry is still exploring the
concepts of parallel programming. Most thread libraries supply only simple
primitive concepts for thread synchronization. These concepts are very
simple, but it is very difficult to use them safely or to provide formal
proofs for constructs built on top of them. There has been a lot of research
into other concepts, such as in "Communicating Sequential Processes."
&Boost.Thread; was designed in iterative steps, with each step providing
the building blocks necessary for the next step and giving the researcher
the tools necessary to explore new concepts in a portable manner.</para>
<para>Given the goal of following a dynamic, iterative approach
&Boost.Thread; shall go through several growth cycles. Each phase in its
development shall be roughly documented here.</para>
</section>
<section>
<title>Phase 1, Synchronization Primitives</title>
<para>Boost is all about providing high quality libraries with
implementations for many platforms. Unfortunately, there's a big problem
faced by developers wishing to supply such high quality libraries, namely
thread-safety. The C++ standard doesn't address threads at all, but real
world programs often make use of native threading support. A portable
library that doesn't address the issue of thread-safety is therefore not
much help to a programmer who wants to use the library in his multithreaded
application. So there's a very great need for portable primitives that will
allow the library developer to create <link
linkend="thread.glossary.thread-safe">thread-safe</link>
implementations. This need far out weighs the need for portable methods to
create and manage threads.</para>
<para>Because of this need, the first phase of &Boost.Thread; focuses
solely on providing portable primitive concepts for thread
synchronization. Types provided in this phase include the
<classname>boost::mutex</classname>,
<classname>boost::try_mutex</classname>,
<classname>boost::timed_mutex</classname>,
<classname>boost::recursive_mutex</classname>,
<classname>boost::recursive_try_mutex</classname>,
<classname>boost::recursive_timed_mutex</classname>, and
<classname>boost::lock_error</classname>. These are considered the "core"
synchronization primitives, though there are others that will be added in
later phases.</para>
</section>
<section id="thread.design.phase2">
<title>Phase 2, Thread Management and Thread Specific Storage</title>
<para>This phase addresses the creation and management of threads and
provides a mechanism for thread specific storage (data associated with a
thread instance). Thread management is a tricky issue in C++, so this
phase addresses only the basic needs of multithreaded program. Later
phases are likely to add additional functionality in this area. This
phase of &Boost.Thread; adds the <classname>boost::thread</classname> and
<classname>boost::thread_specific_ptr</classname> types. With these
additions the &Boost.Thread; library can be considered minimal but
complete.</para>
</section>
<section>
<title>The Next Phase</title>
<para>The next phase will address more advanced synchronization concepts,
such as read/write mutexes and barriers.</para>
</section>
</section>

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<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
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<!ENTITY Boost.Thread "<emphasis role='bold'>Boost.Thread</emphasis>">
<!ENTITY Boost.Build "<emphasis role='bold'>Boost.Build</emphasis>">
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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/exceptions.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="lock_error">
<purpose>
<simpara>The lock_error class defines an exception type thrown
to indicate a locking related error has been detected.</simpara>
</purpose>
<description>
<simpara>Examples of errors indicated by a lock_error exception
include a lock operation which can be determined to result in a
deadlock, or unlock operations attempted by a thread that does
not own the lock.</simpara>
</description>
<inherit access="public">
<type><classname>std::logical_error</classname></type>
</inherit>
<constructor>
<effects><simpara>Constructs a <code>lock_error</code> object.
</simpara></effects>
</constructor>
</class>
<class name="thread_resource_error">
<purpose>
<simpara>The <classname>thread_resource_error</classname> class
defines an exception type that is thrown by constructors in the
&Boost.Thread; library when thread-related resources can not be
acquired.</simpara>
</purpose>
<description>
<simpara><classname>thread_resource_error</classname> is used
only when thread-related resources cannot be acquired; memory
allocation failures are indicated by
<classname>std::bad_alloc</classname>.</simpara>
</description>
<inherit access="public">
<type><classname>std::runtime_error</classname></type>
</inherit>
<constructor>
<effects><simpara>Constructs a <code>thread_resource_error</code>
object.</simpara></effects>
</constructor>
</class>
</namespace>
</header>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, FAQ</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Frequently Asked Questions</h2>
</td>
</tr>
</table>
<hr>
<h2>1. Are lock objects <a href="definitions.html#Thread-safe">thread-safe</a>?</h2>
<p><b>No!</b> Lock objects are not meant to be shared between threads. They are meant to
be short lived objects created on automatic storage within a code block. Any other usage
is just likely to lead to errors and won't really be of actual benefit any way. Share
<a href="mutex_concept.html">mutexes</a>, not locks. For more information see the
<a href="rationale.html#lock_objects">rationale</a> behind the design for lock objects.</p>
<h2>2a. Why was Boost.Threads modeled after (specific library name)?</h2>
<p>It wasn't. Boost.Threads was designed from scratch. Extensive design
discussions involved numerous people representing a wide range of experience across
many platforms. To ensure portability, the initial implements were done in
parallel using POSIX Threads and theWin32 threading API. But the Boost.Threads
design is very much in the spirit of C++, and thus doesn't model such C based
APIs.</p>
<h2>2b. Why wasn't Boost.Threads modeled after (specific library name)?</h2>
<p>Existing C++ libraries either seemed dangerous (often failing to take
advantage of prior art to reduce errors) or had excessive dependencies on
library components unrelated to threading. Existing C libraries couldn't meet
our C++ requirements, and were also missing certain features. For
instance, POSIX threads doesn't support a maximum value for semaphores.
The WIN32 thread API lacks condition variables, even though these are critical
for the important Monitor pattern <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a>.</p>
<h2>3. Why do <a href="mutex_concept.html"> Mutexes</a> have noncopyable semantics?</h2>
<p>To ensure that <a href="definitions.html#Deadlock"> deadlocks</a> don't occur. The only logical form of copy would be to
use some sort of shallow copy semantics in which multiple mutex objects could refer
to the same mutex state. This means that if ObjA has a mutex object as part of its state
and ObjB is copy constructed from it, then when ObjB::foo() locks the mutex it has effectively
locked ObjA as well. This behavior can result in deadlock. Other
copy semantics result in similar problems (if you think you can prove this to
be wrong then supply us with an alternative and we'll reconsider).</p>
<h2>4. How can you prevent <a href="definitions.html#Deadlock"> deadlock</a> from occurring when a thread must lock multiple
mutexes?</h2>
<p>Always lock them in the same order. One easy way of doing this is to use
each mutex's address to determine the order in which they are locked. A future
Boost.Threads concept may wrap this pattern up in a reusable class.</p>
<h2>5. Don't noncopyable <a href="mutex_concept.html"> mutex</a> semantics mean that a
class with a mutex member will be noncopyable as well?</h2>
<p>No, but what it does mean is that the compiler can't generate a copy constructor
and assignment operator, so they will have to be coded explicitly. This is a
<b>good thing</b>, however, since the compiler generated operations would not
be <a href="definitions.html#Thread-safe">thread-safe</a>. The following is a
simple example of a class with copyable semantics and internal synchronization through
a mutex member.</p>
<pre>
class counter
{
public:
// Doesn't need synchronization since there can be no references to *this
// until after it's constructed!
explicit counter(int initial_value)
: m_value(initial_value)
{
}
// We only need to syncronize other for the same reason we don't have to
// synchronize on construction!
counter(const counter&amp; other)
{
boost::mutex::scoped_lock scoped_lock(other.m_mutex);
m_value = other.m_value;
}
// For assignment we need to synchronize both objects!
const counter&amp; operator=(const counter&amp; other)
{
if (this == &amp;other)
return *this;
boost::mutex::scoped_lock lock1(&amp;m_mutex &lt; &amp;other.m_mutex ? m_mutex : other.m_mutex);
boost::mutex::scoped_lock lock2(&amp;m_mutex &gt; &amp;other.m_mutex ? m_mutex : other.m_mutex);
m_value = other.m_value;
return *this;
}
int value() const
{
boost::mutex::scoped_lock scoped_lock(m_mutex);
return m_value;
}
int increment()
{
boost::mutex::scoped_lock scoped_lock(m_mutex);
return ++m_value;
}
private:
mutable boost::mutex m_mutex;
int m_value;
};
</pre>
<h2>6. How can you lock a <a href="mutex_concept.html"> mutex</a> member in a const member function, in order to
implement the Monitor Pattern?</h2>
<p>The Monitor Pattern mutex <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a> should simply be declared as mutable. See the example code above. The internal state of mutex
types could have been made mutable, with all lock calls made via const
functions, but
this does a poor job of documenting the actual semantics. Declaring a mutex member
as mutable clearly documentations the intended semantics.</p>
<h2>7. Why supply <a href="condition.html">condition variables</a> rather than <a href="rationale.html#Events">
event variables</a>?</h2>
<p>Condition variables result in user code much less prone to <a href="definitions.html#Race condition">race
conditions</a> than event variables. See <a href="rationale.html#Events">Rationale</a>
for analysis. Also see <a href="bibliography.html#Hoare-74">[Hoare74]</a>
and <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a>.</p>
<h2>8. Why isn't thread cancellation or termination provided?</h2>
<p>There's a valid need for thread termination, so at some point Boost.Threads
probably will include it, but only after we can find a truly safe (and portable)
mechanism for this concept.</p>
<h2>9. Is it safe for threads to share automatic storage duration (stack)
objects via pointers or references?</h2>
<p>Only if you can guarantee that the lifetime of the stack object will not end
while other threads might still access the object. Thus the safest practice is
to avoid sharing stack objects, particularly in designs where threads are
created and destroyed dynamically. Restrict sharing of stack objects to simple
designs with very clear and unchanging function and thread lifetimes. (Suggested
by Darryl Green).</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->04 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39335" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.faq" last-revision="$Date$">
<title>Frequently Asked Questions</title>
<qandaset>
<qandaentry>
<question>
<para>Are lock objects <link
linkend="thread.glossary.thread-safe">thread safe</link>?</para>
</question>
<answer>
<para><emphasis role="bold">No!</emphasis> Lock objects are not meant to
be shared between threads. They are meant to be short-lived objects
created on automatic storage within a code block. Any other usage is
just likely to lead to errors and won't really be of actual benefit anyway.
Share <link linkend="thread.concepts.mutexes">Mutexes</link>, not
Locks. For more information see the <link
linkend="thread.rationale.locks">rationale</link> behind the
design for lock objects.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why was &Boost.Thread; modeled after (specific library
name)?</para>
</question>
<answer>
<para>It wasn't. &Boost.Thread; was designed from scratch. Extensive
design discussions involved numerous people representing a wide range of
experience across many platforms. To ensure portability, the initial
implements were done in parallel using POSIX Threads and the Win32
threading API. But the &Boost.Thread; design is very much in the spirit
of C++, and thus doesn't model such C based APIs.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why wasn't &Boost.Thread; modeled after (specific library
name)?</para>
</question>
<answer>
<para>Existing C++ libraries either seemed dangerous (often failing to
take advantage of prior art to reduce errors) or had excessive
dependencies on library components unrelated to threading. Existing C
libraries couldn't meet our C++ requirements, and were also missing
certain features. For instance, the WIN32 thread API lacks condition
variables, even though these are critical for the important Monitor
pattern &cite.SchmidtStalRohnertBuschmann;.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why do <link linkend="thread.concepts.mutexes">Mutexes</link>
have noncopyable semantics?</para>
</question>
<answer>
<para>To ensure that <link
linkend="thread.glossary.deadlock">deadlocks</link> don't occur. The
only logical form of copy would be to use some sort of shallow copy
semantics in which multiple mutex objects could refer to the same mutex
state. This means that if ObjA has a mutex object as part of its state
and ObjB is copy constructed from it, then when ObjB::foo() locks the
mutex it has effectively locked ObjA as well. This behavior can result
in deadlock. Other copy semantics result in similar problems (if you
think you can prove this to be wrong then supply us with an alternative
and we'll reconsider).</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>How can you prevent <link
linkend="thread.glossary.deadlock">deadlock</link> from occurring when
a thread must lock multiple mutexes?</para>
</question>
<answer>
<para>Always lock them in the same order. One easy way of doing this is
to use each mutex's address to determine the order in which they are
locked. A future &Boost.Thread; concept may wrap this pattern up in a
reusable class.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Don't noncopyable <link
linkend="thread.concepts.mutexes">Mutex</link> semantics mean that a
class with a mutex member will be noncopyable as well?</para>
</question>
<answer>
<para>No, but what it does mean is that the compiler can't generate a
copy constructor and assignment operator, so they will have to be coded
explicitly. This is a <emphasis role="bold">good thing</emphasis>,
however, since the compiler generated operations would not be <link
linkend="thread.glossary.thread-safe">thread-safe</link>. The following
is a simple example of a class with copyable semantics and internal
synchronization through a mutex member.</para>
<programlisting>
class counter
{
public:
// Doesn't need synchronization since there can be no references to *this
// until after it's constructed!
explicit counter(int initial_value)
: m_value(initial_value)
{
}
// We only need to synchronize other for the same reason we don't have to
// synchronize on construction!
counter(const counter&amp; other)
{
boost::mutex::scoped_lock scoped_lock(other.m_mutex);
m_value = other.m_value;
}
// For assignment we need to synchronize both objects!
const counter&amp; operator=(const counter&amp; other)
{
if (this == &amp;other)
return *this;
boost::mutex::scoped_lock lock1(&amp;m_mutex &lt; &amp;other.m_mutex ? m_mutex : other.m_mutex);
boost::mutex::scoped_lock lock2(&amp;m_mutex &gt; &amp;other.m_mutex ? m_mutex : other.m_mutex);
m_value = other.m_value;
return *this;
}
int value() const
{
boost::mutex::scoped_lock scoped_lock(m_mutex);
return m_value;
}
int increment()
{
boost::mutex::scoped_lock scoped_lock(m_mutex);
return ++m_value;
}
private:
mutable boost::mutex m_mutex;
int m_value;
};
</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>How can you lock a <link
linkend="thread.concepts.mutexes">Mutex</link> member in a const member
function, in order to implement the Monitor Pattern?</para>
</question>
<answer>
<para>The Monitor Pattern &cite.SchmidtStalRohnertBuschmann; mutex
should simply be declared as mutable. See the example code above. The
internal state of mutex types could have been made mutable, with all
lock calls made via const functions, but this does a poor job of
documenting the actual semantics (and in fact would be incorrect since
the logical state of a locked mutex clearly differs from the logical
state of an unlocked mutex). Declaring a mutex member as mutable clearly
documents the intended semantics.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why supply <classname>boost::condition</classname> variables rather than
event variables?</para>
</question>
<answer>
<para>Condition variables result in user code much less prone to <link
linkend="thread.glossary.race-condition">race conditions</link> than
event variables. See <xref linkend="thread.rationale.events" />
for analysis. Also see &cite.Hoare74; and &cite.SchmidtStalRohnertBuschmann;.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why isn't thread cancellation or termination provided?</para>
</question>
<answer>
<para>There's a valid need for thread termination, so at some point
&Boost.Thread; probably will include it, but only after we can find a
truly safe (and portable) mechanism for this concept.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Is it safe for threads to share automatic storage duration (stack)
objects via pointers or references?</para>
</question>
<answer>
<para>Only if you can guarantee that the lifetime of the stack object
will not end while other threads might still access the object. Thus the
safest practice is to avoid sharing stack objects, particularly in
designs where threads are created and destroyed dynamically. Restrict
sharing of stack objects to simple designs with very clear and
unchanging function and thread lifetimes. (Suggested by Darryl
Green).</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why has class semaphore disappeared?</para>
</question>
<answer>
<para>Semaphore was removed as too error prone. The same effect can be
achieved with greater safety by the combination of a mutex and a
condition variable.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why doesn't the thread's ctor take at least a void* to pass any
information along with the function? All other threading libs support
that and it makes Boost.Threads inferiour. </para>
</question>
<answer>
<para>There is no need, because Boost.Threads are superiour! First
thing is that its ctor doesn't take a function but a functor. That
means that you can pass an object with an overloaded operator() and
include additional data as members in that object. Beware though that
this object is copied, use boost::ref to prevent that. Secondly, even
a boost::function&lt;void (void)&gt; can carry parameters, you only have to
use boost::bind() to create it from any function and bind its
parameters.</para>
<para>That is also why Boost.Threads are superiour, because they
don't require you to pass a type-unsafe void pointer. Rather, you can
use the flexible Boost.Functions to create a thread entry out of
anything that can be called.</para>
</answer>
</qandaentry>
</qandaset>
</section>

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@@ -1,304 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<glossary id="thread.glossary" last-revision="$Date$">
<title>Glossary</title>
<para>Definitions are given in terms of the C++ Standard
&cite.ISO98;. References to the standard are in the form [1.2.3/4], which
represents the section number, with the paragraph number following the
"/".</para>
<para>Because the definitions are written in something akin to "standardese",
they can be difficult to understand. The intent isn't to confuse, but rather
to clarify the additional requirements &Boost.Thread; places on a C++
implementation as defined by the C++ Standard.</para>
<glossentry id="thread.glossary.thread">
<glossterm>Thread</glossterm>
<glossdef>
<para>Thread is short for "thread of execution". A thread of execution is
an execution environment [1.9/7] within the execution environment of a C++
program [1.9]. The main() function [3.6.1] of the program is the initial
function of the initial thread. A program in a multithreading environment
always has an initial thread even if the program explicitly creates no
additional threads.</para>
<para>Unless otherwise specified, each thread shares all aspects of its
execution environment with other threads in the program. Shared aspects of
the execution environment include, but are not limited to, the
following:</para>
<itemizedlist>
<listitem><para>Static storage duration (static, extern) objects
[3.7.1].</para></listitem>
<listitem><para>Dynamic storage duration (heap) objects [3.7.3]. Thus
each memory allocation will return a unique addresses, regardless of the
thread making the allocation request.</para></listitem>
<listitem><para>Automatic storage duration (stack) objects [3.7.2]
accessed via pointer or reference from another thread.</para></listitem>
<listitem><para>Resources provided by the operating system. For example,
files.</para></listitem>
<listitem><para>The program itself. In other words, each thread is
executing some function of the same program, not a totally different
program.</para></listitem>
</itemizedlist>
<para>Each thread has its own:</para>
<itemizedlist>
<listitem><para>Registers and current execution sequence (program
counter) [1.9/5].</para></listitem>
<listitem><para>Automatic storage duration (stack) objects
[3.7.2].</para></listitem>
</itemizedlist>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.thread-safe">
<glossterm>Thread-safe</glossterm>
<glossdef>
<para>A program is thread-safe if it has no <link
linkend="thread.glossary.race-condition">race conditions</link>, does
not <link linkend="thread.glossary.deadlock">deadlock</link>, and has
no <link linkend="thread.glossary.priority-failure">priority
failures</link>.</para>
<para>Note that thread-safety does not necessarily imply efficiency, and
than while some thread-safety violations can be determined statically at
compile time, many thread-safety errors can only only be detected at
runtime.</para>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.thread-state">
<glossterm>Thread State</glossterm>
<glossdef>
<para>During the lifetime of a thread, it shall be in one of the following
states:</para>
<table>
<title>Thread States</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>State</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>Ready</entry>
<entry>Ready to run, but waiting for a processor.</entry>
</row>
<row>
<entry>Running</entry>
<entry>Currently executing on a processor. Zero or more threads
may be running at any time, with a maximum equal to the number of
processors.</entry>
</row>
<row>
<entry>Blocked</entry>
<entry>Waiting for some resource other than a processor which is
not currently available, or for the completion of calls to library
functions [1.9/6]. The term "waiting" is synonymous with
"blocked"</entry>
</row>
<row>
<entry>Terminated</entry>
<entry>Finished execution but not yet detached or joined.</entry>
</row>
</tbody>
</tgroup>
</table>
<para>Thread state transitions shall occur only as specified:</para>
<table>
<title>Thread States Transitions</title>
<tgroup cols="3" align="left">
<thead>
<row>
<entry>From</entry>
<entry>To</entry>
<entry>Cause</entry>
</row>
</thead>
<tbody>
<row>
<entry>[none]</entry>
<entry>Ready</entry>
<entry><para>Thread is created by a call to a library function.
In the case of the initial thread, creation is implicit and
occurs during the startup of the main() function [3.6.1].</para></entry>
</row>
<row>
<entry>Ready</entry>
<entry>Running</entry>
<entry><para>Processor becomes available.</para></entry>
</row>
<row>
<entry>Running</entry>
<entry>Ready</entry>
<entry>Thread preempted.</entry>
</row>
<row>
<entry>Running</entry>
<entry>Blocked</entry>
<entry>Thread calls a library function which waits for a resource or
for the completion of I/O.</entry>
</row>
<row>
<entry>Running</entry>
<entry>Terminated</entry>
<entry>Thread returns from its initial function, calls a thread
termination library function, or is canceled by some other thread
calling a thread termination library function.</entry>
</row>
<row>
<entry>Blocked</entry>
<entry>Ready</entry>
<entry>The resource being waited for becomes available, or the
blocking library function completes.</entry>
</row>
<row>
<entry>Terminated</entry>
<entry>[none]</entry>
<entry>Thread is detached or joined by some other thread calling the
appropriate library function, or by program termination
[3.6.3].</entry>
</row>
</tbody>
</tgroup>
</table>
<para>[Note: if a suspend() function is added to the threading library,
additional transitions to the blocked state will have to be added to the
above table.]</para>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.race-condition">
<glossterm>Race Condition</glossterm>
<glossdef>
<para>A race condition is what occurs when multiple threads read from and write
to the same memory without proper synchronization, resulting in an incorrect
value being read or written. The result of a race condition may be a bit
pattern which isn't even a valid value for the data type. A race condition
results in undefined behavior [1.3.12].</para>
<para>Race conditions can be prevented by serializing memory access using
the tools provided by &Boost.Thread;.</para>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.deadlock">
<glossterm>Deadlock</glossterm>
<glossdef>
<para>Deadlock is an execution state where for some set of threads, each
thread in the set is blocked waiting for some action by one of the other
threads in the set. Since each is waiting on the others, none will ever
become ready again.</para>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.starvation">
<glossterm>Starvation</glossterm>
<glossdef>
<para>The condition in which a thread is not making sufficient progress in
its work during a given time interval.</para>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.priority-failure">
<glossterm>Priority Failure</glossterm>
<glossdef>
<para>A priority failure (such as priority inversion or infinite overtaking)
occurs when threads are executed in such a sequence that required work is not
performed in time to be useful.</para>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.undefined-behavior">
<glossterm>Undefined Behavior</glossterm>
<glossdef>
<para>The result of certain operations in &Boost.Thread; is undefined;
this means that those operations can invoke almost any behavior when
they are executed.</para>
<para>An operation whose behavior is undefined can work "correctly"
in some implementations (i.e., do what the programmer thought it
would do), while in other implementations it may exhibit almost
any "incorrect" behavior--such as returning an invalid value,
throwing an exception, generating an access violation, or terminating
the process.</para>
<para>Executing a statement whose behavior is undefined is a
programming error.</para>
</glossdef>
</glossentry>
<glossentry id="thread.glossary.memory-visibility">
<glossterm>Memory Visibility</glossterm>
<glossdef>
<para>An address [1.7] shall always point to the same memory byte,
regardless of the thread or processor dereferencing the address.</para>
<para>An object [1.8, 1.9] is accessible from multiple threads if it is of
static storage duration (static, extern) [3.7.1], or if a pointer or
reference to it is explicitly or implicitly dereferenced in multiple
threads.</para>
<para>For an object accessible from multiple threads, the value of the
object accessed from one thread may be indeterminate or different from the
value accessed from another thread, except under the conditions specified in
the following table. For the same row of the table, the value of an object
accessible at the indicated sequence point in thread A will be determinate
and the same if accessed at or after the indicated sequence point in thread
B, provided the object is not otherwise modified. In the table, the
"sequence point at a call" is the sequence point after the evaluation of all
function arguments [1.9/17], while the "sequence point after a call" is the
sequence point after the copying of the returned value... [1.9/17].</para>
<table>
<title>Memory Visibility</title>
<tgroup cols="2">
<thead>
<row>
<entry>Thread A</entry>
<entry>Thread B</entry>
</row>
</thead>
<tbody>
<row>
<entry>The sequence point at a call to a library thread-creation
function.</entry>
<entry>The first sequence point of the initial function in the new
thread created by the Thread A call.</entry>
</row>
<row>
<entry>The sequence point at a call to a library function which
locks a mutex, directly or by waiting for a condition
variable.</entry>
<entry>The sequence point after a call to a library function which
unlocks the same mutex.</entry>
</row>
<row>
<entry>The last sequence point before thread termination.</entry>
<entry>The sequence point after a call to a library function which
joins the terminated thread.</entry>
</row>
<row>
<entry>The sequence point at a call to a library function which
signals or broadcasts a condition variable.</entry>
<entry>The sequence point after the call to the library function
which was waiting on that same condition variable or signal.</entry>
</row>
</tbody>
</tgroup>
</table>
<para>The architecture of the execution environment and the observable
behavior of the abstract machine [1.9] shall be the same on all
processors.</para>
<para>The latitude granted by the C++ standard for an implementation to
alter the definition of observable behavior of the abstract machine to
include additional library I/O functions [1.9/6] is extended to include
threading library functions.</para>
<para>When an exception is thrown and there is no matching exception handler
in the same thread, behavior is undefined. The preferred behavior is the
same as when there is no matching exception handler in a program
[15.3/9]. That is, terminate() is called, and it is implementation-defined
whether or not the stack is unwound.</para>
</glossdef>
</glossentry>
<section>
<title>Acknowledgements</title>
<para>This document was originally written by Beman Dawes, and then much
improved by the incorporation of comments from William Kempf, who now
maintains the contents.</para>
<para>The visibility rules are based on &cite.Butenhof97;.</para>
</section>
</glossary>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.implementation_notes" last-revision="$Date$">
<title>Implementation Notes</title>
<section id="thread.implementation_notes.win32">
<title>Win32</title>
<para>
In the current Win32 implementation, creating a boost::thread object
during dll initialization will result in deadlock because the thread
class constructor causes the current thread to wait on the thread that
is being created until it signals that it has finished its initialization,
and, as stated in the
<ulink url="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/dllmain.asp">MSDN Library, "DllMain" article, "Remarks" section</ulink>,
"Because DLL notifications are serialized, entry-point functions should not
attempt to communicate with other threads or processes. Deadlocks may occur as a result."
(Also see <ulink url="http://www.microsoft.com/msj/archive/S220.aspx">"Under the Hood", January 1996</ulink>
for a more detailed discussion of this issue).
</para>
<para>
The following non-exhaustive list details some of the situations that
should be avoided until this issue can be addressed:
<itemizedlist>
<listitem>Creating a boost::thread object in DllMain() or in any function called by it.</listitem>
<listitem>Creating a boost::thread object in the constructor of a global static object or in any function called by one.</listitem>
<listitem>Creating a boost::thread object in MFC's CWinApp::InitInstance() function or in any function called by it.</listitem>
<listitem>Creating a boost::thread object in the function pointed to by MFC's _pRawDllMain function pointer or in any function called by it.</listitem>
</itemizedlist>
</para>
</section>
</section>

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<!-- Copyright (c) 2002-2003 Beman Dawes, William E. Kempf.
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
-->
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<head>
<meta http-equiv="refresh" content="0; URL=../../../doc/html/thread.html">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, Index</title>
</head>
<body>
Automatic redirection failed, please go to <a href="../../../doc/html/thread.html">../../../doc/html/thread.html</a>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Documentation Map</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<ul>
<li><a href="overview.html">Overview</a></li>
<li>Class <a href="semaphore.html">semaphore</a></li>
<li><a href="mutex_concept.html">Mutex Concepts</a></li>
<ul>
<li><a href="mutex_concept.html#Mutex">Mutex</a></li>
<li><a href="mutex_concept.html#TryMutex">TryMutex</a></li>
<li><a href="mutex_concept.html#TimedMutex">TimedMutex</a></li>
</ul>
<li>Mutex Classes</li>
<ul>
<li><a href="mutex.html">mutex / try_mutex / timed_mutex</a></li>
<li><a href="recursive_mutex.html">recursive_mutex / recursive_try_mutex / recursive_timed_mutex</a></li>
</ul>
<li><a href="lock_concept.html">Lock Concepts</a></li>
<ul>
<li><a href="lock_concept.html#Lock">Lock</a></li>
<li><a href="lock_concept.html#ScopedLock">ScopedLock</a></li>
<li><a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a></li>
<li><a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a></li>
</ul>
<li>Lock Classes</li>
<ul>
<li><a href="scoped_lock.html">scoped_lock</a></li>
<li><a href="scoped_try_lock.html">scoped_try_lock</a></li>
<li><a href="scoped_timed_lock.html">scoped_timed_lock</a></li>
</ul>
<li>Class <a href="condition.html">condition</a></li>
<li>Class <a href="thread_specific_ptr.html">thread_specific_ptr</a></li>
<li>Class <a href="thread.html">thread</a></li>
<li>Class <a href="thread_group.html">thread_group</a></li>
<li>Class <a href="xtime.html">xtime</a></li>
<li>Class <a href="lock_error.html">lock_error</a></li>
<li>Class <a href="thread_resource_error.html">thread_resource_error</a></li>
<li>Routine <a href="call_once.html">call_once</a></li>
<li><a href="config.html">Configuration Information</a></li>
<li><a href="introduction.html">Introduction to design</a></li>
<li><a href="rationale.html">Rationale for design decisions</a></li>
<li><a href="definitions.html">Definitions</a></li>
<li><a href="faq.html">Frequently Asked Questions</a></li>
<li><a href="bibliography.html">Bibliography</a></li>
<li><a href="acknowledgements.html">Acknowledgements</a></li>
</ul>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->12 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39332" -->
</p>
<p>©<i> Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001</i></p>
<p>Permission to use, copy, modify, distribute and sell this software
and its documentation for any purpose is hereby granted without fee,
provided that the above copyright notice appear in all copies and
that both that copyright notice and this permission notice appear
in supporting documentation. William E. Kempf makes no representations
about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, Introduction</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Introduction</h2>
</td>
</tr>
</table>
<hr>
<h3>Motivation</h3>
<p>With client/server and three-tier architectures becoming common place in today's
world, it's becoming increasingly important for programs to be able to handle parallel
processing. Modern day operating systems usually provide some support for this
through native thread APIs. Unfortunately, writing portable code that makes use
of parallel processing in C++ is made very difficult by a lack of a standard interface
for these native APIs. Further, these APIs are almost universally C APIs and fail to
take advantage of C++'s strengths, or to address C++'s issues.</p>
<p>The <b>Boost.Threads</b> library is an attempt to define a portable interface for writing
parallel processes in C++.</p>
<h3>Goals</h3>
<p>The <b>Boost.Threads</b> library has several goals that should help to set it apart from
other solutions. These goals are listed in order of precedence with full descriptions
below.<p>
<ul>
<li><b>Portability</b>
<p><b>Boost.Threads</b> was designed to be highly portable. The goal is for the
interface to be easily implemented on any platform that supports threads,
and possibly even on platforms without native thread support.</p>
<li><b>Safety</b>
<p><b>Boost.Threads</b> was designed to be as safe as possible. Writing
<a href="definitions.html#Thread-safe">thread-safe</a>
code is very difficult and successful libraries must strive to insulate
the programmer from dangerous constructs as much as possible. This is accomplished
in several ways:</p>
<ul>
<li><p align="left">C++ language features are used make correct usage easy (if possible,
the default) and error-prone impossible or at least more difficult.
For example, see the <a href="mutex_concept.html">Mutex</a> and <a href="lock_concept.html">Lock</a>
designs, and how note how they interact.</p></li>
<li>
<p align="left">Certain traditional concurrent programming features
are considered so error-prone that they are not provided at all. For
example, see the <a href="rationale.html#Events">Events Not Provided</a>
rationale.</p>
</li>
<li>
<p align="left">Dangerous features, or features which may be misused,
are identified as such in the documentation to make users aware of
potential pitfalls. For example, see <a href="semaphore.html#Danger">Semaphore</a>.</p>
</li>
</ul>
<li><b>Flexibility</b>
<p><b>Boost.Threads</b> was designed to be flexible. This goal is often at odds
with <i>safety</i>. When functionality might be compromised by the desire
to keep the interface safe, <b>Boost.Threads</b> has been designed to provide
the functionality, but to make it's use prohibitive for general use.</p>
<li><b>Efficiency</b>
<p><b>Boost.Threads</b> was designed to be as efficient as possible. When building
a library on top of another library there is always a danger that the result
will be so much slower than the "native" API that programmers are inclined
to ignore the higher level API. <b>Boost.Threads</b> was designed to minimize the
chances of this occurring. The interfaces have been crafted to allow an
implementation the greatest chance of being as efficient as possible. This
goal is often at odds with the goal for <i>safety</i>. Every effort was made to
ensure efficient implementations, but when in conflict <i>safety</i> has always taken
precedence.</p>
</li>
</ul>
<h3>Iterative Phases</h3>
<p>Another goal of <b>Boost.Threads</b> was to take a dynamic, iterative
approach in its development. The computing industry is still exploring the concepts of parallel programming.
Most thread libraries supply only simple primitive concepts for thread synchronization.
These concepts are very simple, but they are very difficult to use safely or to provide
formal proofs for constructs built on top of them. Until recently, these primitives
were "state of the art" and the only concepts available to programmers. Recently
there has been a lot of research in other concepts, such as in "Communicating Sequential
Processes." <b>Boost.Threads</b> was designed in iterative steps, providing the building
blocks necessary for the next step, and giving the researcher the tools necessary to
explore new concepts in a portable manner.</p>
<p>Given the goal of following a dynamic, iterative approach <b>Boost.Threads</b> shall go through
several growth cycles. Each phase in its development shall be roughly documented here.</p>
<h4>Phase 1, Synchronization Primitives</h4>
<p>Boost is all about providing high quality libraries with implementations for many platforms.
Unfortunately, there's a big problem faced by developers wishing to supply such high quality
libraries, namely thread-safety. The C++ standard doesn't address threads at all, but real
world programs often make use of native threading support. A portable library that doesn't
address the issue of thread-safety is there for not much help to a programmer who wants to
use the library in his multi-threaded application. So there's a very great need for portable
primitives that will allow the library developer to create <a href="file:///c:/boost/site/libs/thread/doc/definitions.html#Thread-safe">thread-safe</a>
implementations. This
need far out weighs the need for portable methods to create and manage threads.</p>
<p>Because of this need, the first phase of <b>Boost.Threads</b> focuses solely on providing
portable primitive concepts for thread synchronization. Types provided in this phase include
the <A href="semaphore.html">semaphore</a>, <A href="mutex.html">mutex/try_mutex/timed_mutex</a>,
<A href="recursive_mutex.html">recursive_mutex/recursive_try_mutex/recursive_timed_mutex</a>,
<A href="scoped_lock.html">scoped_lock</a>, <A href="scoped_try_lock.html">scoped_try_lock</a>,
<A href="scoped_timed_lock.html">scoped_timed_lock</a> and <A href="lock_error.html">lock_error</a>.
These are considered the "core" synchronization primitives, though there are others that will
be added in later phases.</p>
<h4>Phase 2, Thread Management and Thread Specific Storage</h4>
<p>This phase addresses the creation and management of threads and provides a mechanism for
thread specific storage (data associated with a thread instance). Thread management is a tricky
issue in C++, so this phase addresses only the basic needs of multi-threaded program. Later
phases are likely to add additional functionality in this area. This phase of <b>Boost.Threads</b>
adds the <A href="thread.html">thread</a> and
<A href="thread_specific_ptr.html">thread_specific_ptr</a> types. With these additions
the <b>Boost.Threads</b> library can be considered minimal but complete.</p>
<h4>The Next Phase</h4>
<p>The next phase will address more advanced synchronization concepts, such as read/write mutexes
and barriers.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->03 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39333" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, Lock Concept</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Lock Concepts</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Requirements">Concept Requirements</a><br>
<a href="#Lock">Lock Concept</a><br>
<a href="#ScopedLock">ScopedLock Concept</a><br>
<a href="#ScopedTryLock">ScopedTryLock Concept</a><br>
<a href="#ScopedTimedLock">ScopedTimedLock Concept</a><br>
<a href="#Models">Models</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The lock concepts provide exception safe means for locking and unlocking a
<a href="mutex_concept.html">mutex model</a>. In other words they are an
implementation of the <i>Scoped Locking</i>
<a href="bibliography.html#Schmidt 00">[Schmidt 00]</a> pattern. The
<a href="#ScopedLock">ScopedLock</a> concept, with
<a href="#ScopedTryLock">ScopedTryLock</a> and
<a href="#ScopedTimedLock">ScopedTimedLock</a> refinements, formalize the
requirements.</p>
<p>Lock models are constructed with a reference to a
<a href="mutex_concept.html">mutex model</a> and typically acquire ownership of the
<a href="mutex_concept.html">mutex model</a> by setting its state to locked. They also
ensure ownership is relinquished in the destructor. Lock models also expose functions
to query the lock status and to manually lock and unlock the
<a href="mutex_concept.html">mutex model</a>.</p>
<p>Instances of lock models are meant to be short lived, expected to be used at block
scope only. The lock models are not
<a href="definitions.html#Thread-safe">thread-safe</a>. Lock models must maintain state
to indicate whether or not they've been locked and this state is not protected by any
synchronization concepts. For this reason an instance of a lock model should never be
shared between multiple threads.</p>
<h2>Concept <a name="Requirements">Requirements</a></h2>
<p>[For documentation purposes, portions of the concept requirements are
repeated in the documentation for specific lock classes. Those copies need
to be kept in sync with the requirements here.]</p>
<h3><a name="Lock">Lock</a> Concept</h3>
<p>For a <a href="#ScopedLock"> ScopedLock</a>,
<a href="#ScopedTryLock">ScopedTryLock</a>, or
<a href="#ScopedTimedLock">ScopedTimedLock</a> type <code>L</code> and an object
<code>lk</code> and const object <code>clk</code> of that type, the following expressions
must be well-formed and have the indicated effects.</p>
<p>The Lock concept is used as a base for the <a href="#ScopedLock">ScopedLock</a>,
<a href="#ScopedTryLock">ScopedTryLock</a>, and
<a href="#ScopedTimedLock">ScopedTimedLock</a> refinements. The associated mutex type
is as specified for each of those refinements respectively.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>(&amp;lk)-&gt;~L();</code></td>
<td><code>if (locked()) unlock();</code></td>
</tr>
<tr>
<td valign="top"><code>(&amp;clk)-&gt;operator const void*()</code></td>
<td>Returns type void*, non-zero if if the associated mutex has been locked
by <code>clk</code>, otherwise 0.</td>
</tr>
<tr>
<td valign="top"><code>clk.locked()</code></td>
<td>Returns a <code>bool</code>, <code>(&amp;clk)-&gt;operator const void*() != 0</code></td>
</tr>
<tr>
<td valign="top"><code>lk.lock()</code></td>
<td>Throws lock_error if locked(). If the associated mutex is already locked by some other
thread, places the current thread in the
<a href="definitions.html#State">Blocked</a> state until the associated mutex is
unlocked, after which the current thread is placed in the
<a href="definitions.html#State">Ready</a> state, eventually to be returned to the
<a href="definitions.html#State">Running</a> state.<br>
Postcondition: locked()</td>
</tr>
<tr>
<td valign="top"><code>lk.unlock()</code></td>
<td>If !locked(), throws lock_error, otherwise unlocks the associated mutex.<br>
Postcondition: !locked()</td>
</tr>
</table>
<h3><a name="ScopedLock">ScopedLock</a> Concept</h3>
<p>A ScopedLock must meet the <a href="#Lock">Lock</a> requirements. For a ScopedLock
type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the
<a href="mutex_concept.html#Mutex">Mutex</a> requirements, and an object <code>b</code>
of type <code>bool</code>, the following expressions must be well-formed and have the
indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>L lk(m);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then calls <code>lock()</code></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,b);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then if <code>b</code>, calls <code>lock()</code></td>
</tr>
</table>
<h3><a name="ScopedTryLock">ScopedTryLock</a> Concept</h3>
<p>A ScopedTryLock must meet the <a href="#Lock">Lock</a> requirements. For a
ScopedTryLock type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the
<a href="mutex_concept.html#TryMutex">TryMutex</a> requirements, and an object
<code>b</code> of type <code>bool</code>, the following expressions must be well-formed
and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>L lk(m);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then calls <code>try_lock()</code></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,b);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then if <code>b</code>, calls <code>lock()</code></td>
</tr>
<tr>
<td valign="top"><code>lk.try_lock()</code></td>
<td>If locked(), throws <code>lock_error</code>. Makes a non-blocking attempt to
lock the associated mutex, returning <code>true</code> if the lock attempt is
successful, otherwise <code>false</code>.</td>
</tr>
</table>
<h3><a name="ScopedTimedLock">ScopedTimedLock</a> Concept</h3>
<p>A ScopedTimedLock must meet the <a href="#Lock">Lock</a> requirements. For a
ScopedTimedLock type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the
<a href="mutex_concept.html#TimedMutex">TimedMutex</a> requirements, and an object
<code>b</code> of type <code>bool</code>, and an object <code>t</code> of type
<code><a href="xtime.html">xtime</a></code>, the following expressions must be well-formed and have the indicated
effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,t);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then calls <code>timed_lock(t)</code></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,b);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then if <code>b</code>, calls <code>lock()</code></td>
</tr>
<tr>
<td valign="top"><code>lk.timed_lock(t)</code></td>
<td>If locked(), throws lock_error. Makes a blocking attempt to lock the
associated mutex, and returns <code>true</code> if successful within the specified
time <code>t</code>, otherwise <code>false</code>.</td>
</tr>
</table>
<h2><a name="Models">Models</a></h2>
<p><b>Boost.Threads</b> currently supplies three classes which model lock concepts.</p>
<p>These classes are normally accessed via typedefs of the same name supplied by
a <a href="mutex_concept.html">mutex model</a>.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Concept</b></td>
<td><b>Refines</b></td>
<td><b>Classes Modeling the Concept</b></td>
</tr>
<tr>
<td><a href="#ScopedLock">ScopedLock</a></td>
<td>&nbsp;</td>
<td><a href="scoped_lock.html">scoped_lock</a></td>
</tr>
<tr>
<td><a href="#ScopedTryLock">ScopedTryLock</a></td>
<td><a href="#ScopedLock">ScopedLock</a></td>
<td><a href="scoped_try_lock.html">scoped_try_lock</a> </td>
</tr>
<tr>
<td><a href="#ScopedTimedLock">ScopedTimedLock</a></td>
<td><a href="#ScopedLock">ScopedLock</a></td>
<td><a href="scoped_timed_lock.html">scoped_timed_lock</a></td>
</tr>
</table>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->04 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39335" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, lock_error</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">lock_error</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt>lock_error</tt> class defines an exception type thrown to indicate a
locking related error has been detected. Examples of such errors include a lock
operation which can be determined to result in a deadlock, or unlock operations
attempted by a thread that does not own the lock.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
class lock_error : public std::runtime_error
{
public:
lock_error();
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
lock_error();
</pre>
<p>Constructs a <tt>lock_error</tt> object.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
int main(int, char*[])
{
boost::mutex mutex;
boost::mutex::scoped_lock scoped_lock(mutex);
try
{
boost::mutex::scoped_lock deadlock(mutex);
std::cout &lt;&lt; &quot;lock succeeded&quot; &lt;&lt; std::endl;
}
catch (boost::lock_error&amp; err)
{
std::cout &lt;&lt; err.what() &lt;&lt; &quot; - deadlock occurred.&quot; &lt;&lt; std::endl;
}
return 0;
}
</pre>
<p>The output is:</p>
<pre>
thread lock error - deadlock occurred.
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->10 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39328" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -1,309 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/mutex.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="mutex">
<purpose>
<para>The <classname>mutex</classname> class is a model of the
<link linkend="thread.concepts.Mutex">Mutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>mutex</classname> class is a model of the
<link linkend="thread.concepts.Mutex">Mutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>try_mutex</classname> and <classname>timed_mutex</classname>.</para>
<para>For <link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics, see <classname>recursive_mutex</classname>,
<classname>recursive_try_mutex</classname>, and <classname>recursive_timed_mutex</classname>.
</para>
<para>The <classname>mutex</classname> class supplies the following typedef,
which <link linkend="thread.concepts.lock-models">models</link>
the specified locking strategy:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>mutex</classname> class uses an
<link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
This strategy allows implementations to be as efficient as possible
on any given platform. It is, however, recommended that
implementations include debugging support to detect misuse when
<code>NDEBUG</code> is not defined.</para>
<para>Like all
<link linkend="thread.concepts.mutex-models">mutex models</link>
in &Boost.Thread;, <classname>mutex</classname> leaves the
<link linkend="thread.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="try_mutex">
<purpose>
<para>The <classname>try_mutex</classname> class is a model of the
<link linkend="thread.concepts.TryMutex">TryMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>try_mutex</classname> class is a model of the
<link linkend="thread.concepts.TryMutex">TryMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>mutex</classname> and <classname>timed_mutex</classname>.</para>
<para>For <link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics, see <classname>recursive_mutex</classname>,
<classname>recursive_try_mutex</classname>, and <classname>recursive_timed_mutex</classname>.
</para>
<para>The <classname>try_mutex</classname> class supplies the following typedefs,
which <link linkend="thread.concepts.lock-models">model</link>
the specified locking strategies:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>try_mutex</classname> class uses an
<link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>try_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
This strategy allows implementations to be as efficient as possible
on any given platform. It is, however, recommended that
implementations include debugging support to detect misuse when
<code>NDEBUG</code> is not defined.</para>
<para>Like all
<link linkend="thread.concepts.mutex-models">mutex models</link>
in &Boost.Thread;, <classname>try_mutex</classname> leaves the
<link linkend="thread.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>try_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>try_mutex</classname> object.
</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="timed_mutex">
<purpose>
<para>The <classname>timed_mutex</classname> class is a model of the
<link linkend="thread.concepts.TimedMutex">TimedMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>timed_mutex</classname> class is a model of the
<link linkend="thread.concepts.TimedMutex">TimedMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>mutex</classname> and <classname>try_mutex</classname>.</para>
<para>For <link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics, see <classname>recursive_mutex</classname>,
<classname>recursive_try_mutex</classname>, and <classname>recursive_timed_mutex</classname>.
</para>
<para>The <classname>timed_mutex</classname> class supplies the following typedefs,
which <link linkend="thread.concepts.lock-models">model</link>
the specified locking strategies:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
<row>
<entry>scoped_timed_lock</entry>
<entry><link linkend="thread.concepts.ScopedTimedLock">ScopedTimedLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>timed_mutex</classname> class uses an
<link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>timed_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
This strategy allows implementations to be as efficient as possible
on any given platform. It is, however, recommended that
implementations include debugging support to detect misuse when
<code>NDEBUG</code> is not defined.</para>
<para>Like all
<link linkend="thread.concepts.mutex-models">mutex models</link>
in &Boost.Thread;, <classname>timed_mutex</classname> leaves the
<link linkend="thread.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>timed_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>timed_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
</namespace>
</header>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, mutex</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG alt="C++ Boost" src="../../../c++boost.gif" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">mutex<br>
try_mutex<br>
timed_mutex</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#mutex Synopsis">Class mutex Synopsis</a><br>
<a href="#mutex Members">Class mutex Members</a><br>
<a href="#try_mutex Synopsis">Class try_mutex Synopsis</a><br>
<a href="#try_mutex Members">Class try_mutex Members</a><br>
<a href="#timed_mutex Synopsis">Class timed_mutex Synopsis</a><br>
<a href="#timed_mutex Members">Class timed_mutex Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt><a href="#mutex Synopsis">mutex</a></tt>, <tt><a href="#try_mutex Synopsis">try_mutex</a></tt> and <tt><a href="#timed_mutex Synopsis">timed_mutex</a></tt> classes define full featured
models of the <a href="mutex_concept.html#Mutex">Mutex</a>, <a href="mutex_concept.html#TryMutex">TryMutex</a>,
and <a href="mutex_concept.html#TimedMutex">TimedMutex</a> concepts. These types should be used to
non-recursively synchronize access to
shared resources. For recursive locking mechanics, see <a href="recursive_mutex.html">recursive
mutexes</a>.</p>
<p>Each class supplies one or more typedefs for lock types which model matching
lock concepts. For the best possible performance you should use the mutex class that supports
the minimum set of lock
types that you need.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Mutex Class</b></td>
<td><b>Lock name</b></td>
<td><b>Implementation defined Lock Type</b></td>
<td><b>&nbsp;Lock Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#mutex Synopsis"><code>mutex</code></a></td>
<td valign="middle"><code>scoped_lock</code></td>
<td valign="middle"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a></td>
</tr>
<tr>
<td valign="top"><tt><a href="#try_mutex Synopsis">try_mutex</a></tt> </td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock</code></td>
<td valign="middle"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;try_mutex&gt;<br>
</code></a><code><a href="scoped_try_lock.html">boost::detail::thread::scoped_try_lock&lt;try_mutex&gt;</a></code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a></td>
</tr>
<tr>
<td valign="top"><code><a href="#timed_mutex Synopsis">timed_mutex</a></code> </td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock<br>
scoped_timed_lock</code></td>
<td valign="middle"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;timed_mutex&gt;</code></a><br>
<code><a href="scoped_try_lock.html">boost::</a></code><a href="scoped_try_lock.html"><code>detail::thread::scoped_try_lock&lt;timed_mutex&gt;</code></a><br>
<code><a href="scoped_timed_lock.html">boost::</a></code><a href="scoped_timed_lock.html"><code>detail::thread::scoped_timed_lock&lt;timed_mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a><br>
<a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a></td>
</tr>
</table>
<p>The <tt>mutex</tt>, <tt>try_mutex</tt> and <tt>timed_mutex</tt> classes use an <tt>Unspecified</tt>
<A href="mutex_concept.html#LockingStrategies">locking strategy</a>, so attempts to recursively lock
them or attempts to unlock them by threads that don't own a lock on them result in <b>undefined behavior</b>.
This strategy allows implementations to be as efficient as possible on any given platform. It is, however,
recommended that implementations include debugging support to detect misuse when <tt>NDEBUG</tt> is
not defined.</p>
<p>Like all the <b>Boost.Threads</b> <A href="mutex_concept.html">mutex models</a>, the <tt>mutex</tt>,
<tt>try_mutex</tt> and <tt>timed_mutex</tt> leave the
<A href="mutex_concept.html#SchedulingPolicies">scheduling policy</a> as <tt>Unspecified</tt>.
Programmers should assume that threads waiting for a lock on objects of these types
acquire
the lock in a random order, even though the specific behavior for a given platform may be different.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
</pre>
<h2>Class <a name="mutex Synopsis"> mutex Synopsis</a></h2>
<pre>
namespace boost
{
class mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
mutex();
~mutex();
};
}
</pre>
<h2>
Class <a name="mutex Members">mutex Members</a>
</h2>
<hr>
<h3>Constructor</h3>
<pre>
mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</p>
<hr>
<h2>
Class <a name="try_mutex Synopsis">try_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class try_mutex : private boost::noncopyable // Exposition only.
// Class try_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
try_mutex();
~try_mutex();
};
}
</pre>
<h2>Class <a name="try_mutex Members">try_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
try_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~try_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</p>
<hr>
<h2>
Class <a name="timed_mutex Synopsis">timed_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class timed_mutex : private boost::noncopyable // Exposition only.
// Class timed_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_timed_lock;
timed_mutex();
~timed_mutex();
};
}
</pre>
<h2>Class <a name="timed_mutex Members">timed_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
timed_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~timed_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
boost::mutex io_mutex; // The iostreams are not guaranteed to be <a href="file:///c:/boost/site/libs/thread/doc/definitions.html#Thread-safe">thread-safe</a>!
class counter
{
public:
counter() : count(0) { }
int increment() {
boost::mutex::scoped_lock scoped_lock(mutex);
return ++count;
}
private:
boost::mutex mutex;
int count;
};
counter c;
void change_count(void*)
{
int i = c.increment();
boost::mutex::scoped_lock scoped_lock(io_mutex);
std::cout &lt;&lt; &quot;count == &quot; &lt;&lt; i &lt;&lt; std::endl;
}
int main(int, char*[])
{
const int num_threads = 4;
boost::thread_group thrds;
for (int i=0; i &lt; num_threads; ++i)
thrds.create_thread(&amp;change_count, 0);
thrds.join_all();
return 0;
}
</pre>
<p>The output is:</p>
<pre>
count == 1
count == 2
count == 3
count == 4
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, Mutex Concept</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Mutex Concepts</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#LockingStrategies">Locking Strategies</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Recursive">Recursive</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#CheckedStrategy">Checked</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UncheckedStrategy">Unchecked</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UnspecifiedStrategy">Unspecified</a><br>
<a href="#SchedulingPolicies">Scheduling Policies</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#FIFO">FIFO</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Priority Driven">Priority Driven</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UndefinedScheduling">Undefined</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UnspecifiedScheduling">Unspecified</a><br>
<a href="#Requirements">Concept Requirements</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Mutex">Mutex Concept</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#TryMutex">TryMutex Concept</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#TimedMutex">TimedMutex Concept</a><br>
<a href="#Models">Models</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>A mutex (short for mutual-exclusion) concept serializes access to
a resource shared between multiple threads. The <a href="#Mutex">Mutex</a>
concept, with <a href="#TryMutex">TryMutex</a> and <a href="#TimedMutex">TimedMutex</a>
refinements, formalize the requirements. A model that implements Mutex and its
refinements has two states: <b> locked</b> and <b>unlocked</b>. Before using a
shared resource, a thread locks a Boost.Threads mutex model object,
insuring <a href="definitions.html#Thread-safe">thread-safe</a> access to the shared
resource. When use of the shared resource is complete, the thread unlocks the mutex
model object, allowing another thread to acquire the lock and use the shared resource.</p>
<p>Traditional C thread APIs, like Pthreads or the Windows thread APIs, expose
functions to lock and unlock a mutex model. This is dangerous since it's easy to forget
to unlock a locked mutex. When the flow of control is complex, with multiple return
points, the likelihood of forgetting to unlock a mutex model would become even greater.
When exceptions are thrown, it becomes nearly impossible to ensure that the mutex is
unlocked properly when using these traditional API's. The result is
<a href="definitions.html#Deadlock">deadlock</a>.</p>
<p>Many C++ threading libraries use a pattern known as <i>Scoped Locking</i>
<a href="bibliography.html#Schmidt 00">[Schmidt 00]</a> to free the programmer from the
need to explicitly lock and unlock mutexes. With this pattern, a
<A href="lock_concept.html">lock concept</A> is employed where the lock model's
constructor locks the associated mutex model and the destructor automatically does the
unlocking. The <b>Boost.Threads</b> library takes this pattern to the extreme in that
lock concepts are the only way to lock and unlock a mutex model: lock and unlock
functions are not exposed by any <b>Boost.Threads </b>mutex models. This helps to
ensure safe usage patterns, especially when code throws exceptions.</p>
<h2><a name="LockingStrategies">Locking Strategies</a></h2>
<p>Every mutex model follows one of several locking strategies. These strategies
define the semantics for the locking operation when the calling thread already
owns a lock on the mutex model.</p>
<h3><a name="Recursive">Recursive</a></h3>
<p>With a recursive locking strategy when a thread attempts to acquire a lock on
the mutex model for which it already owns a lock, the operation is successful.
Note the distinction between a thread, which may have multiple locks outstanding
on a recursive mutex, and a lock object, which even for a recursive mutex cannot
have its lock() function called multiple times without first calling unlock().</p>
<p>Internally a lock count is maintained and the owning thread must unlock the
mutex model the same number of times that it's locked it before the mutex model's
state returns to unlocked. Since mutex models in <b>Boost.Threads</b> expose
locking functionality only through lock concepts, a thread will always unlock a mutex
model the same number of times that it locked it. This helps to eliminate a whole set
of errors typically found in traditional C style thread APIs.</p>
<p>Classes <A href="recursive_mutex.html">recursive_mutex</A>,
<A href="recursive_mutex.html">recursive_try_mutex</A> and
<A href="recursive_mutex.html">recursive_timed_mutex</A> use this locking strategy.</p>
<h3><a name="CheckedStrategy">Checked</a></h3>
<p>With a checked locking strategy when a thread attempts to acquire a lock on
the mutex model for which the thread already owns a lock, the operation will fail with
some sort of error indication. Further, attempts by a thread to unlock a mutex
that was not locked by the thread will also return some sort of error indication.
In <b>Boost.Threads</b>, an exception of type <A href="lock_error.html">lock_error</A>
would be thrown in these cases.</p>
<p><b>Boost.Threads</b> does not currently provide any mutex models that use this
strategy.</p>
<h3><a name="UncheckedStrategy">Unchecked</a></h3>
<p>With an unchecked locking strategy when a thread attempts to acquire a lock
on the mutex model for which the thread already owns a lock the operation will
<a href="definitions.html#Deadlock">deadlock</a>. In general this locking strategy is
less safe than a checked or recursive strategy, but it's also a faster strategy and so
is employed by many libraries.</p>
<p><b>Boost.Threads</b> does not currently provide any mutex models that use this
strategy.</p>
<h3><a name="UnspecifiedStrategy">Unspecified</a></h3>
<p>With an unspecified locking strategy, when a thread attempts to acquire a lock
on a mutex model for which the thread already owns a lock the operation results in
<b>undefined behavior</b>. When a mutex model has an unspecified locking strategy the
programmer must assume that the mutex model instead uses an unchecked strategy.</p>
<p>In general a mutex model with an unspecified locking strategy is unsafe, and it
requires programmer discipline to use the mutex model properly. However, this strategy
allows an implementation to be as fast as possible with no restrictions on its
implementation. This is especially true for portable implementations that wrap the
native threading support of a platform. For this reason, the classes
<A href="mutex.html">mutex</A>, <A href="mutex.html">try_mutex</A> and
<A href="mutex.html">timed_mutex</A> use this locking strategy despite the lack of
safety.</p>
<h2><a name="SchedulingPolicies">Scheduling Policies</a></h2>
<p>Every mutex model follows one of several scheduling policies. These policies
define the semantics when the mutex model is unlocked and there is more than one
thread waiting to acquire a lock. In other words, the policy defines which waiting
thread shall acquire the lock.</p>
<h3><a name="FIFO">FIFO</a></h3>
<p>With a FIFO scheduling policy, threads waiting for the lock will acquire it in
a first come first serve order (or First In First Out). This can help prevent a
high priority thread from starving lower priority threads that are also waiting
on the mutex lock.</p>
<h3><a name="Priority Driven">Priority Driven</a></h3>
<p>With a Priority Driven scheduling policy, the thread with the highest priority
acquires the lock. Note that this means that low-priority threads may never acquire
the lock if the mutex model has high contention and there is always at least one
high-priority thread waiting. This is known as thread starvation. When multiple threads
of the same priority are waiting on the mutex lock one of the other scheduling
priorities will determine which thread shall acquire the lock.</p>
<h3><a name="UndefinedScheduling">Undefined</a></h3>
<p>Threads acquire the lock in no particular order. Users should assume that
low-priority threads may wait indefinitely, and that threads of the same
priority acquire the lock in essentially random order.</p>
<h3><a name="UnspecifiedScheduling">Unspecified</a></h3>
<p>The mutex model does not specify which scheduling policy is used. The programmer
must assume that an undefined scheduling policy is used. In order to ensure portability,
all <b>Boost.Threads</b> mutex models use an unspecified scheduling policy.</p>
<h2>Concept <a name="Requirements">Requirements</a></h2>
<h3><a name="Mutex">Mutex</a> Concept</h3>
<p>A Mutex object has two states: locked and unlocked. Mutex object state can only be
determined by an object meeting the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements and constructed for the Mutex object.</p>
<p>A Mutex is <a href="../../utility/utility.htm#Class noncopyable">noncopyable</a>.</p>
<p>For a Mutex type M and an object m of that type, the following expressions must be
well-formed and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>M m;</code></td>
<td>Constructs a mutex object m. Post-condition: m is unlocked.</td>
</tr>
<tr>
<td><code>(&amp;m)-&gt;~M();</code></td>
<td>Precondition: m is unlocked. Destroys a mutex object m.</td>
</tr>
<tr>
<td><code>M::scoped_lock</code></td>
<td>A type meeting the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements.</td>
</tr>
</table>
<h3><a name="TryMutex">TryMutex</a> Concept</h3>
<p>A TryMutex must meet the <a href="#Mutex"> Mutex</a> requirements. In addition, for a
TryMutex type M and an object m of that type, the following expressions must be
well-formed and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>M::scoped_try_lock</code></td>
<td>A type meeting the <a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a>
requirements.</td>
</tr>
</table>
<h3><a name="TimedMutex">TimedMutex</a> Concept</h3>
<p>A TimedMutex must meet the <a href="#TryMutex"> TryMutex</a> requirements. In addition, for a
TimedMutex type M and an object m of that type, the following
expressions must be well-formed and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>M::scoped_timed_lock</code></td>
<td>A type meeting the <a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a>
requirements.</td>
</tr>
</table>
<h2><a name="Models">Models</a></h2>
<p> <b>Boost.Threads</b> currently supplies six classes which model mutex
concepts.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Concept</b></td>
<td><b>Refines</b></td>
<td><b>Classes Modeling the Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#Mutex">Mutex</a></td>
<td valign="top">&nbsp;</td>
<td><A href="mutex.html">mutex</A><br>
<A href="recursive_mutex.html">recursive_mutex</A></td>
</tr>
<tr>
<td valign="top"><a href="#TryMutex">TryMutex</a></td>
<td valign="top"><a href="#Mutex">Mutex</a></td>
<td><A href="mutex.html">try_mutex<br>
</A><A href="recursive_mutex.html">recursive_try_mutex</A> </td>
</tr>
<tr>
<td valign="top"><a href="#TimedMutex">TimedMutex</a></td>
<td valign="top"><a href="#TryMutex">TryMutex</a></td>
<td><A href="mutex.html">timed_mutex<br>
</A><A href="recursive_mutex.html">recursive_timed_mutex</A></td>
</tr>
</table>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->03 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39333" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</A>
2001 all rights reserved.</i></p>
</body>
</html>

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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:mutex_types Mutex Types]
[section:mutex Class `mutex`]
#include <boost/thread/mutex.hpp>
class mutex:
boost::noncopyable
{
public:
mutex();
~mutex();
void lock();
bool try_lock();
void unlock();
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
typedef unique_lock<mutex> scoped_lock;
typedef unspecified-type scoped_try_lock;
};
__mutex__ implements the __lockable_concept__ to provide an exclusive-ownership mutex. At most one thread can own the lock on a given
instance of __mutex__ at any time. Multiple concurrent calls to __lock_ref__, __try_lock_ref__ and __unlock_ref__ shall be permitted.
[section:nativehandle Member function `native_handle()`]
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
[variablelist
[[Effects:] [Returns an instance of `native_handle_type` that can be used with platform-specific APIs to manipulate the underlying
implementation. If no such instance exists, `native_handle()` and `native_handle_type` are not present.]]
[[Throws:] [Nothing.]]
]
[endsect]
[endsect]
[section:try_mutex Typedef `try_mutex`]
#include <boost/thread/mutex.hpp>
typedef mutex try_mutex;
__try_mutex__ is a `typedef` to __mutex__, provided for backwards compatibility with previous releases of boost.
[endsect]
[section:timed_mutex Class `timed_mutex`]
#include <boost/thread/mutex.hpp>
class timed_mutex:
boost::noncopyable
{
public:
timed_mutex();
~timed_mutex();
void lock();
void unlock();
bool try_lock();
bool timed_lock(system_time const & abs_time);
template<typename TimeDuration>
bool timed_lock(TimeDuration const & relative_time);
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
typedef unique_lock<timed_mutex> scoped_timed_lock;
typedef unspecified-type scoped_try_lock;
typedef scoped_timed_lock scoped_lock;
};
__timed_mutex__ implements the __timed_lockable_concept__ to provide an exclusive-ownership mutex. At most one thread can own the
lock on a given instance of __timed_mutex__ at any time. Multiple concurrent calls to __lock_ref__, __try_lock_ref__,
__timed_lock_ref__, __timed_lock_duration_ref__ and __unlock_ref__ shall be permitted.
[section:nativehandle Member function `native_handle()`]
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
[variablelist
[[Effects:] [Returns an instance of `native_handle_type` that can be used with platform-specific APIs to manipulate the underlying
implementation. If no such instance exists, `native_handle()` and `native_handle_type` are not present.]]
[[Throws:] [Nothing.]]
]
[endsect]
[endsect]
[section:recursive_mutex Class `recursive_mutex`]
#include <boost/thread/recursive_mutex.hpp>
class recursive_mutex:
boost::noncopyable
{
public:
recursive_mutex();
~recursive_mutex();
void lock();
bool try_lock();
void unlock();
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
typedef unique_lock<recursive_mutex> scoped_lock;
typedef unspecified-type scoped_try_lock;
};
__recursive_mutex__ implements the __lockable_concept__ to provide an exclusive-ownership recursive mutex. At most one thread can
own the lock on a given instance of __recursive_mutex__ at any time. Multiple concurrent calls to __lock_ref__, __try_lock_ref__ and
__unlock_ref__ shall be permitted. A thread that already has exclusive ownership of a given __recursive_mutex__ instance can call
__lock_ref__ or __try_lock_ref__ to acquire an additional level of ownership of the mutex. __unlock_ref__ must be called once for
each level of ownership acquired by a single thread before ownership can be acquired by another thread.
[section:nativehandle Member function `native_handle()`]
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
[variablelist
[[Effects:] [Returns an instance of `native_handle_type` that can be used with platform-specific APIs to manipulate the underlying
implementation. If no such instance exists, `native_handle()` and `native_handle_type` are not present.]]
[[Throws:] [Nothing.]]
]
[endsect]
[endsect]
[section:recursive_try_mutex Typedef `recursive_try_mutex`]
#include <boost/thread/recursive_mutex.hpp>
typedef recursive_mutex recursive_try_mutex;
__recursive_try_mutex__ is a `typedef` to __recursive_mutex__, provided for backwards compatibility with previous releases of boost.
[endsect]
[section:recursive_timed_mutex Class `recursive_timed_mutex`]
#include <boost/thread/recursive_mutex.hpp>
class recursive_timed_mutex:
boost::noncopyable
{
public:
recursive_timed_mutex();
~recursive_timed_mutex();
void lock();
bool try_lock();
void unlock();
bool timed_lock(system_time const & abs_time);
template<typename TimeDuration>
bool timed_lock(TimeDuration const & relative_time);
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
typedef unique_lock<recursive_timed_mutex> scoped_lock;
typedef unspecified-type scoped_try_lock;
typedef scoped_lock scoped_timed_lock;
};
__recursive_timed_mutex__ implements the __timed_lockable_concept__ to provide an exclusive-ownership recursive mutex. At most one
thread can own the lock on a given instance of __recursive_timed_mutex__ at any time. Multiple concurrent calls to __lock_ref__,
__try_lock_ref__, __timed_lock_ref__, __timed_lock_duration_ref__ and __unlock_ref__ shall be permitted. A thread that already has
exclusive ownership of a given __recursive_timed_mutex__ instance can call __lock_ref__, __timed_lock_ref__,
__timed_lock_duration_ref__ or __try_lock_ref__ to acquire an additional level of ownership of the mutex. __unlock_ref__ must be
called once for each level of ownership acquired by a single thread before ownership can be acquired by another thread.
[section:nativehandle Member function `native_handle()`]
typedef platform-specific-type native_handle_type;
native_handle_type native_handle();
[variablelist
[[Effects:] [Returns an instance of `native_handle_type` that can be used with platform-specific APIs to manipulate the underlying
implementation. If no such instance exists, `native_handle()` and `native_handle_type` are not present.]]
[[Throws:] [Nothing.]]
]
[endsect]
[endsect]
[include shared_mutex_ref.qbk]
[endsect]

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/once.hpp"
last-revision="$Date$">
<macro name="BOOST_ONCE_INIT">
<purpose>The <functionname>call_once</functionname> function and
<code>once_flag</code> type (statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>) can be used to run a
routine exactly once. This can be used to initialize data in a
<link linkend="thread.glossary.thread-safe">thread-safe</link>
manner.</purpose>
<description>The implementation-defined macro
<macroname>BOOST_ONCE_INIT</macroname> is a constant value used to
initialize <code>once_flag</code> instances to indicate that the
logically associated routine has not been run yet. See
<functionname>call_once</functionname> for more details.</description>
</macro>
<namespace name="boost">
<typedef name="once_flag">
<purpose>The <functionname>call_once</functionname> function and
<code>once_flag</code> type (statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>) can be used to run a
routine exactly once. This can be used to initialize data in a
<link linkend="thread.glossary.thread-safe">thread-safe</link>
manner.</purpose>
<description>The implementation-defined type <code>once_flag</code>
is used as a flag to insure a routine is called only once.
Instances of this type should be statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>. See
<functionname>call_once</functionname> for more details.
</description>
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<function name="call_once">
<purpose>The <functionname>call_once</functionname> function and
<code>once_flag</code> type (statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>) can be used to run a
routine exactly once. This can be used to initialize data in a
<link linkend="thread.glossary.thread-safe">thread-safe</link>
manner.</purpose>
<description>
<para>Example usage is as follows:</para>
<para>
<programlisting>//Example usage:
boost::once_flag once = BOOST_ONCE_INIT;
void init()
{
//...
}
void thread_proc()
{
boost::call_once(once, &amp;init);
}</programlisting>
</para></description>
<parameter name="flag">
<paramtype>once_flag&amp;</paramtype>
</parameter>
<parameter name="func">
<paramtype>Function func</paramtype>
</parameter>
<effects>As if (in an atomic fashion):
<code>if (flag == BOOST_ONCE_INIT) func();</code>. If <code>func()</code> throws an exception, it shall be as if this
thread never invoked <code>call_once</code></effects>
<postconditions><code>flag != BOOST_ONCE_INIT</code> unless <code>func()</code> throws an exception.
</postconditions>
</function>
</namespace>
</header>

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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:once One-time Initialization]
`boost::call_once` provides a mechanism for ensuring that an initialization routine is run exactly once without data races or deadlocks.
[section:once_flag Typedef `once_flag`]
#include <boost/thread/once.hpp>
typedef platform-specific-type once_flag;
#define BOOST_ONCE_INIT platform-specific-initializer
Objects of type `boost::once_flag` shall be initialized with `BOOST_ONCE_INIT`:
boost::once_flag f=BOOST_ONCE_INIT;
[endsect]
[section:call_once Non-member function `call_once`]
#include <boost/thread/once.hpp>
template<typename Callable>
void call_once(once_flag& flag,Callable func);
[variablelist
[[Requires:] [`Callable` is `CopyConstructible`. Copying `func` shall have no side effects, and the effect of calling the copy shall
be equivalent to calling the original. ]]
[[Effects:] [Calls to `call_once` on the same `once_flag` object are serialized. If there has been no prior effective `call_once` on
the same `once_flag` object, the argument `func` (or a copy thereof) is called as-if by invoking `func()`, and the invocation of
`call_once` is effective if and only if `func()` returns without exception. If an exception is thrown, the exception is
propagated to the caller. If there has been a prior effective `call_once` on the same `once_flag` object, the `call_once` returns
without invoking `func`. ]]
[[Synchronization:] [The completion of an effective `call_once` invocation on a `once_flag` object, synchronizes with
all subsequent `call_once` invocations on the same `once_flag` object. ]]
[[Throws:] [`thread_resource_error` when the effects cannot be achieved. or any exception propagated from `func`.]]
]
void call_once(void (*func)(),once_flag& flag);
This second overload is provided for backwards compatibility. The effects of `call_once(func,flag)` shall be the same as those of
`call_once(flag,func)`.
[endsect]
[endsect]

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost.Threads Overview</title>
</head>
<body>
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Overview</h2>
</td>
</tr>
</table>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Dangers">Dangers</a><br>
<a href="#Library">C++ Standard Library usage</a><br>
<a href="#Common">Common requirements</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>Boost.Threads allows C++ programs to execute as multiple, asynchronous,
independent, threads-of-execution. Each thread has its own machine state
including program instruction counter and registers. Programs which execute as
multiple threads are call multi-threaded programs to distinguish them from
traditional single-threaded programs. <a href="definitions.html">Definitions</a>
gives a more complete description of the multi-threading execution environment.</p>
<p>Multi-threading provides several advantages:</p>
<ul>
<li>Programs which would otherwise block waiting for some external event can
continue to respond if the blocking operation is placed in a separate
thread.&nbsp; Multi-threading is usually an absolute requirement for these
programs.</li>
</ul>
<ul>
<li>Well-designed multi-threaded programs may execute faster than single-threaded
programs, particularly on multi-processor hardware.&nbsp;
Note, however, that poorly-designed multi-threaded programs are often slower
that single-threaded programs.</li>
</ul>
<ul>
<li>Some program designs may be easier to formulate using a multi-threaded
approach.
After all, the real world is asynchronous!&nbsp;</li>
</ul>
<h2><a name="Dangers">Dangers</a></h2>
<p>Beyond the errors which can occur in single-threaded programs, multi-threaded
programs are subject to additional errors:</p>
<ul>
<li><a href="definitions.html#Race condition">Race conditions</a>.
<li><a href="definitions.html#Deadlock">Deadlock</a> (sometimes called
&quot;deadly embrace&quot;)
<li><a href="definitions.html#Priority failure">Priority failures</a>
(priority inversion, infinite overtaking, starvation, etc.)</li>
</ul>
<p>Every multi-threaded program must be designed carefully to avoid race
conditions and deadlock.&nbsp; These aren't rare or exotic failures - they are
virtually guaranteed to occur unless multi-threaded code is designed to avoid
them.&nbsp; Priority failures are somewhat less common, but are none-the-less
serious.</p>
<p>The <a href="introduction.html">Boost.Threads design</a> attempts to minimize
these errors, but they will still occur unless the programmer proactively
designs to avoid them.</p>
<h3>Testing and debugging considerations</h3>
<p>Multi-threaded programs are non-deterministic. In other words, the same
program with the same input data may follow different execution paths each time
it is invoked.&nbsp; That can make testing and debugging a nightmare:</p>
<ul>
<li>Failures are often not repeatable.
<li>Probe effect causes debuggers to produce very different results from
non-debug uses.
<li>Debuggers require special support to show thread state.
<li>Tests on a single processor system may give no indication of serious
errors which would appear on multiprocessor systems, and visa versa. Thus test
cases should include a varying number of processors.&nbsp;</li>
<li>For programs which create a varying number of threads according to
workload, tests which don't span the full range of possibilities may miss
serious errors.</li>
</ul>
<h3>Getting a head start</h3>
<p>Although it might appear that multi-threaded programs are inherently
unreliable, many reliable multi-threaded programs do exist. Multi-threading
techniques are known which lead to reliable programs.</p>
<p>Design patterns for reliable multi-threaded programs, including the important
<i>monitor</i> pattern, are presented in <cite>Pattern-Oriented Software Architecture Volume 2 - Patterns for
Concurrent and Networked Objects</cite> [<a href="bibliography.html#Schmidt-00">Schmidt
00</a>].&nbsp; Many important multi-threading programming considerations
(independent of threading library) are discussed in <cite>Programming with
POSIX Threads</cite> [<a href="bibliography.html#Butenhof-97">Butenhof 97</a>].</p>
<p>Reading and study first yields a head start toward designing reliable
multi-threaded programs.</p>
<h2><a name="Library">C++ Standard Library usage in multi-threaded programs</a></h2>
<h3>Runtime libraries</h3>
<p><b>Warning:</b> Multi-threaded programs such as those using <b>Boost.Threads</b> must link to
<a href="definitions.html#Thread-safe">thread-safe</a> versions of all runtime
libraries used by the program, including the runtime library for the C++
Standard Library. Otherwise <a href="definitions.html#Race condition">race
conditions</a> will occur when multiple threads simultaneously execute runtime
library functions for <i>new</i>, <i>delete</i>, or other language features
which imply shared state.&nbsp;&nbsp;</p>
<h3>Potentially non-thread-safe functions</h3>
<p>Certain C++ Standard Library functions inherited from C are particular
problems because they hold internal state between calls:</p>
<ul>
<li>rand</li>
<li>strtok</li>
<li>asctime</li>
<li>ctime&nbsp;</li>
<li>gmtime</li>
<li>localtime</li>
</ul>
<p>It is possible to write thread-safe implementations of these by using <a href="thread_specific_ptr.html">thread-specific
storage</a>, and several C++ compiler vendors do just that.&nbsp; The technique
is well-know and is explained in [<a href="bibliography.html#Butenhof-97">Buttenhof-97</a>].</p>
<p>But at least one vendor (HP-UX) does not provide thread-safe implementations
of the above functions in their otherwise thread-safe runtime library.&nbsp;
Instead they provide replacement functions with different names and arguments.</p>
<p><b>Recommendation:</b> For the most portable, yet thread-safe code, use Boost
replacements for the problem functions.&nbsp; See the <a href="../../random/index.html">Boost
Random Number Library</a> and <a href="../../tokenizer/index.htm">Boost
Tokenizer Library</a>.</p>
<h2><a name="Common">Common</a> requirements for all Boost.Threads components</h2>
<h3>Exceptions</h3>
<p> <b>Boost.Threads</b> destructors never throw exceptions. Unless otherwise
specified, other <b>Boost.Threads</b>
functions that do not have an exception-specification may throw implementation-defined exceptions.</p>
<p>In particular, <b>Boost.Threads</b> reports failure to allocate storage by throwing an exception of type
std::bad_alloc, or a class derived from std::bad_alloc, failure to obtain
thread resources other than memory by throwing an exception of type <a href="thread_resource_error.html">boost::thread_resource_error</a>,
and certain lock related failures by throwing an exception of type <a href="lock_error.html">boost::lock_error</a></p>
<p><b>Rationale: </b>Follows the C++ Standard Library practice of allowing all
functions except destructors or other specified functions to throw exceptions on
errors.</p>
<h3><a name="NonCopyable">NonCopyable</a> requirement</h3>
<p><b>Boost.Threads</b> classes documented as meeting the NonCopyable requirement disallow copy
construction and copy assignment. For the sake of exposition, the synopsis of
such classes show private derivation from <a href="../../utility/utility.htm">boost::noncopyable</a>.
Users should not depend on this derivation, however, as implementations are free
to meet the NonCopyable requirement in other ways.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->12 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39332" -->
</p>
<p>© Copyright 2001 Beman Dawes</p>
</body>
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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:overview Overview]
__boost_thread__ enables the use of multiple threads of execution with shared data in portable C++ code. It provides classes and
functions for managing the threads themselves, along with others for synchronizing data between the threads or providing separate
copies of data specific to individual threads.
The __boost_thread__ library was originally written and designed by William E. Kempf. This version is a major rewrite designed to
closely follow the proposals presented to the C++ Standards Committee, in particular
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2497.html N2497],
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2320.html N2320],
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2184.html N2184],
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2139.html N2139], and
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2094.html N2094]
In order to use the classes and functions described here, you can
either include the specific headers specified by the descriptions of
each class or function, or include the master thread library header:
#include <boost/thread.hpp>
which includes all the other headers in turn.
[endsect]

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.overview" last-revision="$Date$">
<title>Overview</title>
<section id="thread.introduction">
<title>Introduction</title>
<para>&Boost.Thread; allows C++ programs to execute as multiple,
asynchronous, independent threads-of-execution. Each thread has its own
machine state including program instruction counter and registers. Programs
which execute as multiple threads are called multithreaded programs to
distinguish them from traditional single-threaded programs. The <link
linkend="thread.glossary">glossary</link> gives a more complete description
of the multithreading execution environment.</para>
<para>Multithreading provides several advantages:
<itemizedlist>
<listitem>
<para>Programs which would otherwise block waiting for some external
event can continue to respond if the blocking operation is placed in a
separate thread. Multithreading is usually an absolute requirement for
these programs.</para>
</listitem>
<listitem>
<para>Well-designed multithreaded programs may execute faster than
single-threaded programs, particularly on multiprocessor hardware.
Note, however, that poorly-designed multithreaded programs are often
slower than single-threaded programs.</para>
</listitem>
<listitem>
<para>Some program designs may be easier to formulate using a
multithreaded approach. After all, the real world is
asynchronous!</para>
</listitem>
</itemizedlist></para>
</section>
<section>
<title>Dangers</title>
<section>
<title>General considerations</title>
<para>Beyond the errors which can occur in single-threaded programs,
multithreaded programs are subject to additional errors:
<itemizedlist>
<listitem>
<para><link linkend="thread.glossary.race-condition">Race
conditions</link></para>
</listitem>
<listitem>
<para><link linkend="thread.glossary.deadlock">Deadlock</link>
(sometimes called "deadly embrace")</para>
</listitem>
<listitem>
<para><link linkend="thread.glossary.priority-failure">Priority
failures</link> (priority inversion, infinite overtaking, starvation,
etc.)</para>
</listitem>
</itemizedlist></para>
<para>Every multithreaded program must be designed carefully to avoid these
errors. These aren't rare or exotic failures - they are virtually guaranteed
to occur unless multithreaded code is designed to avoid them. Priority
failures are somewhat less common, but are nonetheless serious.</para>
<para>The <link linkend="thread.design">&Boost.Thread; design</link>
attempts to minimize these errors, but they will still occur unless the
programmer proactively designs to avoid them.</para>
<note>Please also see <xref linkend="thread.implementation_notes"/>
for additional, implementation-specific considerations.</note>
</section>
<section>
<title>Testing and debugging considerations</title>
<para>Multithreaded programs are non-deterministic. In other words, the
same program with the same input data may follow different execution
paths each time it is invoked. That can make testing and debugging a
nightmare:
<itemizedlist>
<listitem>
<para>Failures are often not repeatable.</para>
</listitem>
<listitem>
<para>Probe effect causes debuggers to produce very different results
from non-debug uses.</para>
</listitem>
<listitem>
<para>Debuggers require special support to show thread state.</para>
</listitem>
<listitem>
<para>Tests on a single processor system may give no indication of
serious errors which would appear on multiprocessor systems, and visa
versa. Thus test cases should include a varying number of
processors.</para>
</listitem>
<listitem>
<para>For programs which create a varying number of threads according
to workload, tests which don't span the full range of possibilities
may miss serious errors.</para>
</listitem>
</itemizedlist></para>
</section>
<section>
<title>Getting a head start</title>
<para>Although it might appear that multithreaded programs are inherently
unreliable, many reliable multithreaded programs do exist. Multithreading
techniques are known which lead to reliable programs.</para>
<para>Design patterns for reliable multithreaded programs, including the
important <emphasis>monitor</emphasis> pattern, are presented in
<emphasis>Pattern-Oriented Software Architecture Volume 2 - Patterns for
Concurrent and Networked Objects</emphasis>
&cite.SchmidtStalRohnertBuschmann;. Many important multithreading programming
considerations (independent of threading library) are discussed in
<emphasis>Programming with POSIX Threads</emphasis> &cite.Butenhof97;.</para>
<para>Doing some reading before attempting multithreaded designs will
give you a head start toward reliable multithreaded programs.</para>
</section>
</section>
<section>
<title>C++ Standard Library usage in multithreaded programs</title>
<section>
<title>Runtime libraries</title>
<para>
<emphasis role="bold">Warning:</emphasis> Multithreaded programs such as
those using &Boost.Thread; must link to <link
linkend="thread.glossary.thread-safe">thread-safe</link> versions of
all runtime libraries used by the program, including the runtime library
for the C++ Standard Library. Failure to do so will cause <link
linkend="thread.glossary.race-condition">race conditions</link> to occur
when multiple threads simultaneously execute runtime library functions for
<code>new</code>, <code>delete</code>, or other language features which
imply shared state.</para>
</section>
<section>
<title>Potentially non-thread-safe functions</title>
<para>Certain C++ Standard Library functions inherited from C are
particular problems because they hold internal state between
calls:
<itemizedlist>
<listitem>
<para><code>rand</code></para>
</listitem>
<listitem>
<para><code>strtok</code></para>
</listitem>
<listitem>
<para><code>asctime</code></para>
</listitem>
<listitem>
<para><code>ctime</code></para>
</listitem>
<listitem>
<para><code>gmtime</code></para>
</listitem>
<listitem>
<para><code>localtime</code></para>
</listitem>
</itemizedlist></para>
<para>It is possible to write thread-safe implementations of these by
using thread specific storage (see
<classname>boost::thread_specific_ptr</classname>), and several C++
compiler vendors do just that. The technique is well-know and is explained
in &cite.Butenhof97;.</para>
<para>But at least one vendor (HP-UX) does not provide thread-safe
implementations of the above functions in their otherwise thread-safe
runtime library. Instead they provide replacement functions with
different names and arguments.</para>
<para><emphasis role="bold">Recommendation:</emphasis> For the most
portable, yet thread-safe code, use Boost replacements for the problem
functions. See the <libraryname>Boost Random Number Library</libraryname>
and <libraryname>Boost Tokenizer Library</libraryname>.</para>
</section>
</section>
<section>
<title>Common guarantees for all &Boost.Thread; components</title>
<section>
<title>Exceptions</title>
<para>&Boost.Thread; destructors never
throw exceptions. Unless otherwise specified, other
&Boost.Thread; functions that do not have
an exception-specification may throw implementation-defined
exceptions.</para>
<para>In particular, &Boost.Thread;
reports failure to allocate storage by throwing an exception of type
<code>std::bad_alloc</code> or a class derived from
<code>std::bad_alloc</code>, failure to obtain thread resources other than
memory by throwing an exception of type
<classname>boost::thread_resource_error</classname>, and certain lock
related failures by throwing an exception of type
<classname>boost::lock_error</classname>.</para>
<para><emphasis role="bold">Rationale:</emphasis> Follows the C++ Standard
Library practice of allowing all functions except destructors or other
specified functions to throw exceptions on errors.</para>
</section>
<section>
<title>NonCopyable requirement</title>
<para>&Boost.Thread; classes documented as
meeting the NonCopyable requirement disallow copy construction and copy
assignment. For the sake of exposition, the synopsis of such classes show
private derivation from <classname>boost::noncopyable</classname>. Users
should not depend on this derivation, however, as implementations are free
to meet the NonCopyable requirement in other ways.</para>
</section>
</section>
</section>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, rationale</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Rationale</h2>
</td>
</tr>
</table>
<hr>
<p>This page explains the rationale behind various design decisions in the <b> Boost.Threads</b>
library. Having the rationale documented here should explain how we arrived at the current
design as well as prevent future rehashing of discussions and thought processes that have
already occurred. It can also give users a lot of insight into the design process required
for this library.</p>
<h2><a name="library">Rationale for the Creation of Boost.Threads</a></h2>
<p>Processes often have a degree of "potential parallelism" and it can often be more intuitive
to design systems with this in mind. Further, these parallel processes can result in more responsive
programs. The benefits for multi-threaded programming are quite well known to most modern programmers,
yet the C++ language doesn't directly support this concept.</p>
<p>Many platforms support multi-threaded programming despite the fact that the language doesn't support
it. They do this through external libraries, which are, unfortunately, platform specific. POSIX has
tried to address this problem through the standardization of a "pthread" library. However, this
is a standard only on POSIX platforms, so its portability is limited.</p>
<p>Another problem with POSIX and other platform specific thread libraries is that they are
almost universally C based libraries. This leaves several C++ specific issues unresolved, such
as what happens when an exception is thrown in a thread. Further, there are some C++ concepts,
such as destructors, that can make usage much easier than what's available in a C library.</p>
<p>What's truly needed is C++ language support for threads. However, the C++ standards committee needs
existing practice or a good proposal as a starting point for adding this to the standard.</p>
<p>The Boost.Threads library was developed to provide a C++ developer with a portable interface
for writing multi-threaded programs on numerous platforms. There's a hope that the library can
be the basis for a more detailed proposal for the C++ standards committee to consider for inclusion
in the next C++ standard.</p>
<h2><a name="primitives">Rationale for the Low Level Primitives Supported in Boost.Threads</a></h2>
<p>The Boost.Threads library supplies a set of low level primitives for writing multi-threaded
programs, such as semaphores, mutexes and condition variables. In fact, the first release of
Boost.Threads supports only these low level primitives. However, computer
science research has shown
that use of these primitives is difficult since there's no way to mathematically prove that a
usage pattern is correct, meaning it doesn't result in race conditions or deadlocks. There
are several algebras (such as CSP, CCS and Join calculus) that have been developed to help write
provably correct parallel processes. In order to prove the correctness these processes must
be coded using higher level abstractions. So why does Boost.Threads support the lower level
concepts?</p>
<p>The reason is simple: the higher level concepts need to be implemented using at least some
of the lower level concepts. So having portable lower level concepts makes it easier to develop
the higher level concepts and will allow researchers to experiment with various techniques.</p>
<p>Beyond this theoretical application of higher level concepts, however, the fact remains that
many multi-threaded programs are written using only the lower level concepts, so they are
useful in and of themselves, even if it's hard to prove that their usage is correct. Since
many users will be familiar with these lower level concepts but be unfamiliar with any of the
higher level concepts there's also an argument for accessibility.</p>
<h2><a name="lock_objects">Rationale for the Lock Design</a></h2>
<p>Programmers who are used to multi-threaded programming issues will quickly note that the
Boost.Thread's design for mutex lock concepts is not <a href="file:///c:/boost/site/libs/thread/doc/definitions.html#Thread-safe">thread-safe</a>
(this is clearly documented
as well). At first this may seem like a serious design flaw. Why have a multi-threading primitive
that's not thread-safe itself?</p>
<p>A lock object is not a synchronization primitive. A lock object's sole responsibility is
to ensure that a mutex is both locked and unlocked in a manner that won't result in the common
error of locking a mutex and then forgetting to unlock it. This means that instances of a
lock object are only going to be created, at least in theory, within block scope and won't
be shared between threads. Only the mutex objects will be created outside of block scope and/or
shared between threads. Though it's possible to create a lock object outside of block scope and
to share it between threads to do so would not be a typical usage. Nor are there any cases when
such usage would be required.</p>
<p>Lock objects must maintain some state information. In order to allow a program to determine
if a try_lock or timed_lock was successful the lock object must retain state indicating
the success or failure of the call made in its constructor. If a lock object were to have
such state and remain thread-safe it would need to synchronize access to the state information
which would result in roughly doubling the time of most operations. Worse, since checking
the state can occur only by a call after construction we'd have a race condition if the lock
object were shared between threads.</p>
<p>So, to avoid the overhead of synchronizing access to the state information and to avoid
the race condition the Boost.Threads library simply does nothing to make lock objects thread-safe. Instead, sharing a lock object between threads results in undefined behavior. Since the
only proper usage of lock objects is within block scope this isn't a problem, and so long
as the lock object is properly used there's no danger of any multi-threading issues.</p>
<h2><a name="thread">Rationale for Non-copyable Thread Type</a></h2>
<p>Programmers who are used to C libraries for multi-threaded programming are likely to
wonder why Boost.Threads uses a non-copyable design for <a href="thread.html">boost::thread</a>. After all, the C
thread types are copyable, and you often have a need for copying them within user code.
However, careful comparison of C designs to C++ designs shows a flaw in this logic.</p>
<p>All C types are copyable. It is, in fact, not possible to make a non-copyable type in
C. For this reason types that represent system resources in C are often designed to behave
very similarly to a pointer to dynamic memory. There's an API for acquiring the resource
and an API for releasing the resources. For memory we have pointers as the type and
alloc/free for the acquisition and release APIs. For files we have FILE* as the type
and fopen/fclose for the acquisition and release APIs. You can freely copy instances of the
types but must manually manage the lifetime of the actual resource through the acquisition
and release APIs.</p>
<p>C++ designs recognize that the acquisition and release APIs are error prone and try
to eliminate possible errors by acquiring the resource in the constructor and releasing it
in the destructor. The best example of such a design is the std::iostream set of classes
which can represent the same resource as the FILE* type in C. A file is opened in the
std::fstream's constructor and closed in its destructor. However, if an iostream were
copyable it could lead to a file being closed twice, an obvious error, so the std::iostream
types are noncopyable by design. This is the same design used by boost::thread, which
is a simple and easy to understand design that's consistent with other C++ standard types.</p>
<p>During the design of boost::thread it was pointed out that it would be possible to allow
it to be a copyable type if some form of "reference management" were used, such as ref-counting
or ref-lists, and many argued for a boost::thread_ref design instead. The reasoning was
that copying "thread" objects was a typical need in the C libraries, and so presumably would
be in the C++ libraries as well. It was also thought that implementations could provide
more efficient reference management then wrappers (such as boost::shared_ptr) around a noncopyable
thread concept. Analysis of whether or not these arguments would hold true don't appear to
bear them out. To illustrate the analysis we'll first provide pseudo-code illustrating the six
typical usage patterns of a thread object.</p>
<h3>1. Simple creation of a thread.</h3>
<pre>
void foo()
{
create_thread(&amp;bar);
}
</pre>
<h3>2. Creation of a thread that's later joined.</h3>
<pre>
void foo()
{
thread = create_thread(&amp;bar);
join(thread);
}
</pre>
<h3>3. Simple creation of several threads in a loop.</h3>
<pre>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
create_thread(&amp;bar);
}
</pre>
<h3>4. Creation of several threads in a loop which are later joined.</h3>
<pre>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = create_thread(&amp;bar);
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i].join();
}
</pre>
<h3>5. Creation of a thread whose ownership is passed to another object/method.</h3>
<pre>
void foo()
{
thread = create_thread(&amp;bar);
manager.owns(thread);
}
</pre>
<h3>6. Creation of a thread whose ownership is shared between multiple objects.</h3>
<pre>
void foo()
{
thread = create_thread(&amp;bar);
manager1.add(thread);
manager2.add(thread);
}
</pre>
<p>Of these usage patterns there's only one that requires reference management (number 6).
Hopefully it's fairly obvious that this usage pattern simply won't occur as often as the
other usage patterns. So there really isn't a "typical need" for a thread concept, though
there is some need.</p>
<p>Since the need isn't typical we must use different criteria for deciding on either a
thread_ref or thread design. Possible criteria include ease of use and performance. So let's
analyze both of these carefully.</p>
<p>With ease of use we can look at existing experience. The standard C++ objects that
represent a system resource, such as std::iostream, are noncopyable, so we know that C++
programmers must at least be experienced with this design. Most C++ developers are also
used to smart pointers such as boost::shared_ptr, so we know they can at least adapt to
a thread_ref concept with little effort. So existing experience isn't going to lead us
to a choice.</p>
<p>The other thing we can look at is how difficult it is to use both types for the six usage
patterns above. If we find it overly difficult to use a concept for any of the usage patterns
there would be a good argument for choosing the other design. So we'll code all six usage
patterns using both designs.</p>
<h3>1.</h3>
<pre>
void foo()
{
thread thrd(&amp;bar);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
}
</pre>
<h3>2.</h3>
<pre>
void foo()
{
thread thrd(&amp;bar);
thrd.join();
}
void foo()
{
thread_ref thrd =
create_thread(&amp;bar);thrd-&gt;join();
}
</pre>
<h3>3.</h3>
<pre>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread thrd(&amp;bar);
}
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread_ref thrd = create_thread(&amp;bar);
}
</pre>
<h3>4.</h3>
<pre>
void foo()
{
std::auto_ptr&lt;thread&gt; threads[NUM_THREADS];
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = std::auto_ptr&lt;thread&gt;(new thread(&amp;bar));
for (int i= 0; i&lt;NUM_THREADS;
++i)threads[i]-&gt;join();
}
void foo()
{
thread_ref threads[NUM_THREADS];
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = create_thread(&amp;bar);
for (int i= 0; i&lt;NUM_THREADS;
++i)threads[i]-&gt;join();
}
</pre>
<h3>5.</h3>
<pre>
void foo()
{
thread thrd* = new thread(&amp;bar);
manager.owns(thread);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager.owns(thrd);
}
</pre>
<h3>6.</h3>
<pre>
void foo()
{
boost::shared_ptr&lt;thread&gt; thrd(new thread(&amp;bar));
manager1.add(thrd);
manager2.add(thrd);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager1.add(thrd);
manager2.add(thrd);
}
</pre>
<p>This shows the usage patterns being nearly identical in complexity for both designs.
The only actual added complexity occurs because of the use of operator new in (4), (5)
and (6) and the use of std::auto_ptr and boost::shared_ptr in (4) and (6) respectively.
However, that's not really much added complexity, and C++ programmers are used to using
these idioms any way. Some may dislike the presence of operator new in user code,
but this can be eliminated by proper design of higher level concepts, such as the
boost::thread_group class that simplifies example (4) down to:</p>
<pre>
void foo()
{
thread_group threads;
for (int i=0; i&lt;NUM_THREADS; ++i)
threads.create_thread(&amp;bar);
threads.join_all();
}
</pre>
<p>So ease of use is really a wash and not much help in picking a design.</p>
<p>So what about performance? If you look at the above code examples we can analyze
the theoretical impact to performance that both designs have. For (1) we can see that
platforms that don't have a ref-counted native thread type (POSIX, for instance) will
be impacted by a thread_ref design. Even if the native thread type is ref-counted there
may be an impact if more state information has to be maintained for concepts foreign
to the native API, such as clean up stacks for Win32 implementations. For (2) the
performance impact will be identical to (1). The same for (3). For (4) things get a
little more interesting and we find that theoretically at least the thread_ref may
perform faster since the thread design requires dynamic memory allocation/deallocation.
However, in practice there may be dynamic allocation for the thread_ref design as well,
it will just be hidden from the user. As long as the implementation has to do dynamic
allocations the thread_ref loses again because of the reference management. For (5)
we see the same impact as we do for (4). For (6) we still have a possible impact
to the thread design because of dynamic allocation but thread_ref no longer suffers
because of it's reference management, and in fact, theoretically at least, the thread_ref
may do a better job of managing the references. All of this indicates that thread wins
for (1), (2) and (3), with (4) and (5) the winner depends on the implementation and the platform
but the thread design probably has a better chance, and with (6) it will again
depend on the implementation and platform but this time we favor thread_ref slightly.
Given all of this it's a narrow margin, but the thread design prevails.</p>
<p>Given this analysis, and the fact that noncopyable objects for system resources are
the normal designs that C++ programmers are used to dealing with, the Boost.Threads
library has gone with a noncopyable design.</p>
<h2>Rationale for not providing <i><a name="Events">Event</a> Variables</i></h2>
<p><i>Event variables </i>are simply far too error-prone.&nbsp; <a href="condition.html">Condition
variables</a> are a much safer alternative.</p>
<p>[Note that Graphical User Interface <i>events</i> are a different concept,
and are not what is being discussed here.]</p>
<p>Event variables were one of the first synchronization primitives. They are
still used today, for example, in the native Windows multithreading API.</p>
<p>Yet both respected computer science researchers and experienced
multithreading practitioners believe event variables are so inherently
error-prone that they should never be used, and thus should not be part of a
multithreading library.</p>
<p>Per Brinch Hansen <a href="bibliography.html#Brinch-Hansen-73">[Brinch Hansen
73]</a> analyzed event variables in some detail, pointing out [emphasis his]
that &quot;<i>event operations force the programmer to be aware of the relative
speeds of the sending and receiving processes</i>&quot;. His summary:</p>
<blockquote>
<p>We must therefore conclude that event variables of the previous type are
impractical for system design. <i>The effect of an interaction between two
processes must be independent of the speed at which it is carried out.</i></p>
</blockquote>
<p>Experienced programmers using the Windows platform today
report that event variables are a continuing source of errors, even after previous
bad experiences caused them to be very careful in their use of event
variables.&nbsp; Overt problems can be avoided, for example, by teaming the
event variable with a mutex, but that may just convert a <a href="definitions.html#Race condition">race
condition</a> into another problem, such as excessive resource use. One of the most
distressing aspects of the experience reports is the claim that many defects are
latent.&nbsp; That is, the programs appear to work correctly, but contain
hidden timing dependencies which will cause them to fail when environmental
factors or usage patterns change, altering relative thread timings.</p>
<p>The decision to exclude event variables from Boost.Threads has been
surprising to some Windows programmers.&nbsp; They have written programs which
work using event variables, and wonder what the problem is.&nbsp; It seems
similar to the &quot;goto considered harmful&quot; controversy of 30 years ago.
It isn't that events, like gotos, can't be made to work, but rather that
virtually all programs using alternatives will be easier to write, debug,
read, maintain, and be less likely to contain latent defects.</p>
<p>[Rationale provided by Beman Dawes]</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->17 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34355" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</A>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -1,438 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.rationale" last-revision="$Date$">
<title>Rationale</title>
<para>This page explains the rationale behind various design decisions in the
&Boost.Thread; library. Having the rationale documented here should explain
how we arrived at the current design as well as prevent future rehashing of
discussions and thought processes that have already occurred. It can also give
users a lot of insight into the design process required for this
library.</para>
<section id="thread.rationale.Boost.Thread">
<title>Rationale for the Creation of &Boost.Thread;</title>
<para>Processes often have a degree of "potential parallelism" and it can
often be more intuitive to design systems with this in mind. Further, these
parallel processes can result in more responsive programs. The benefits for
multithreaded programming are quite well known to most modern programmers,
yet the C++ language doesn't directly support this concept.</para>
<para>Many platforms support multithreaded programming despite the fact that
the language doesn't support it. They do this through external libraries,
which are, unfortunately, platform specific. POSIX has tried to address this
problem through the standardization of a "pthread" library. However, this is
a standard only on POSIX platforms, so its portability is limited.</para>
<para>Another problem with POSIX and other platform specific thread
libraries is that they are almost universally C based libraries. This leaves
several C++ specific issues unresolved, such as what happens when an
exception is thrown in a thread. Further, there are some C++ concepts, such
as destructors, that can make usage much easier than what's available in a C
library.</para>
<para>What's truly needed is C++ language support for threads. However, the
C++ standards committee needs existing practice or a good proposal as a
starting point for adding this to the standard.</para>
<para>The &Boost.Thread; library was developed to provide a C++ developer
with a portable interface for writing multithreaded programs on numerous
platforms. There's a hope that the library can be the basis for a more
detailed proposal for the C++ standards committee to consider for inclusion
in the next C++ standard.</para>
</section>
<section id="thread.rationale.primitives">
<title>Rationale for the Low Level Primitives Supported in &Boost.Thread;</title>
<para>The &Boost.Thread; library supplies a set of low level primitives for
writing multithreaded programs, such as mutexes and condition variables. In
fact, the first release of &Boost.Thread; supports only these low level
primitives. However, computer science research has shown that use of these
primitives is difficult since it's difficult to mathematically prove that a
usage pattern is correct, meaning it doesn't result in race conditions or
deadlocks. There are several algebras (such as CSP, CCS and Join calculus)
that have been developed to help write provably correct parallel
processes. In order to prove the correctness these processes must be coded
using higher level abstractions. So why does &Boost.Thread; support the
lower level concepts?</para>
<para>The reason is simple: the higher level concepts need to be implemented
using at least some of the lower level concepts. So having portable lower
level concepts makes it easier to develop the higher level concepts and will
allow researchers to experiment with various techniques.</para>
<para>Beyond this theoretical application of higher level concepts, however,
the fact remains that many multithreaded programs are written using only the
lower level concepts, so they are useful in and of themselves, even if it's
hard to prove that their usage is correct. Since many users will be familiar
with these lower level concepts but unfamiliar with any of the higher
level concepts, supporting the lower level concepts provides
greater accessibility.</para>
</section>
<section id="thread.rationale.locks">
<title>Rationale for the Lock Design</title>
<para>Programmers who are used to multithreaded programming issues will
quickly note that the &Boost.Thread; design for mutex lock concepts is not
<link linkend="thread.glossary.thread-safe">thread-safe</link> (this is
clearly documented as well). At first this may seem like a serious design
flaw. Why have a multithreading primitive that's not thread-safe
itself?</para>
<para>A lock object is not a synchronization primitive. A lock object's sole
responsibility is to ensure that a mutex is both locked and unlocked in a
manner that won't result in the common error of locking a mutex and then
forgetting to unlock it. This means that instances of a lock object are only
going to be created, at least in theory, within block scope and won't be
shared between threads. Only the mutex objects will be created outside of
block scope and/or shared between threads. Though it's possible to create a
lock object outside of block scope and to share it between threads, to do so
would not be a typical usage (in fact, to do so would likely be an
error). Nor are there any cases when such usage would be required.</para>
<para>Lock objects must maintain some state information. In order to allow a
program to determine if a try_lock or timed_lock was successful the lock
object must retain state indicating the success or failure of the call made
in its constructor. If a lock object were to have such state and remain
thread-safe it would need to synchronize access to the state information
which would result in roughly doubling the time of most operations. Worse,
since checking the state can occur only by a call after construction, we'd
have a race condition if the lock object were shared between threads.</para>
<para>So, to avoid the overhead of synchronizing access to the state
information and to avoid the race condition, the &Boost.Thread; library
simply does nothing to make lock objects thread-safe. Instead, sharing a
lock object between threads results in undefined behavior. Since the only
proper usage of lock objects is within block scope this isn't a problem, and
so long as the lock object is properly used there's no danger of any
multithreading issues.</para>
</section>
<section id="thread.rationale.non-copyable">
<title>Rationale for NonCopyable Thread Type</title>
<para>Programmers who are used to C libraries for multithreaded programming
are likely to wonder why &Boost.Thread; uses a noncopyable design for
<classname>boost::thread</classname>. After all, the C thread types are
copyable, and you often have a need for copying them within user
code. However, careful comparison of C designs to C++ designs shows a flaw
in this logic.</para>
<para>All C types are copyable. It is, in fact, not possible to make a
noncopyable type in C. For this reason types that represent system resources
in C are often designed to behave very similarly to a pointer to dynamic
memory. There's an API for acquiring the resource and an API for releasing
the resource. For memory we have pointers as the type and alloc/free for
the acquisition and release APIs. For files we have FILE* as the type and
fopen/fclose for the acquisition and release APIs. You can freely copy
instances of the types but must manually manage the lifetime of the actual
resource through the acquisition and release APIs.</para>
<para>C++ designs recognize that the acquisition and release APIs are error
prone and try to eliminate possible errors by acquiring the resource in the
constructor and releasing it in the destructor. The best example of such a
design is the std::iostream set of classes which can represent the same
resource as the FILE* type in C. A file is opened in the std::fstream's
constructor and closed in its destructor. However, if an iostream were
copyable it could lead to a file being closed twice, an obvious error, so
the std::iostream types are noncopyable by design. This is the same design
used by boost::thread, which is a simple and easy to understand design
that's consistent with other C++ standard types.</para>
<para>During the design of boost::thread it was pointed out that it would be
possible to allow it to be a copyable type if some form of "reference
management" were used, such as ref-counting or ref-lists, and many argued
for a boost::thread_ref design instead. The reasoning was that copying
"thread" objects was a typical need in the C libraries, and so presumably
would be in the C++ libraries as well. It was also thought that
implementations could provide more efficient reference management than
wrappers (such as boost::shared_ptr) around a noncopyable thread
concept. Analysis of whether or not these arguments would hold true doesn't
appear to bear them out. To illustrate the analysis we'll first provide
pseudo-code illustrating the six typical usage patterns of a thread
object.</para>
<section id="thread.rationale.non-copyable.simple">
<title>1. Use case: Simple creation of a thread.</title>
<programlisting>
void foo()
{
create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="thread.rationale.non-copyable.joined">
<title>2. Use case: Creation of a thread that's later joined.</title>
<programlisting>
void foo()
{
thread = create_thread(&amp;bar);
join(thread);
}
</programlisting>
</section>
<section id="thread.rationale.non-copyable.loop">
<title>3. Use case: Simple creation of several threads in a loop.</title>
<programlisting>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="thread.rationale.non-copyable.loop-join">
<title>4. Use case: Creation of several threads in a loop which are later joined.</title>
<programlisting>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = create_thread(&amp;bar);
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i].join();
}
</programlisting>
</section>
<section id="thread.rationale.non-copyable.pass">
<title>5. Use case: Creation of a thread whose ownership is passed to another object/method.</title>
<programlisting>
void foo()
{
thread = create_thread(&amp;bar);
manager.owns(thread);
}
</programlisting>
</section>
<section id="thread.rationale.non-copyable.shared">
<title>6. Use case: Creation of a thread whose ownership is shared between multiple
objects.</title>
<programlisting>
void foo()
{
thread = create_thread(&amp;bar);
manager1.add(thread);
manager2.add(thread);
}
</programlisting>
</section>
<para>Of these usage patterns there's only one that requires reference
management (number 6). Hopefully it's fairly obvious that this usage pattern
simply won't occur as often as the other usage patterns. So there really
isn't a "typical need" for a thread concept, though there is some
need.</para>
<para>Since the need isn't typical we must use different criteria for
deciding on either a thread_ref or thread design. Possible criteria include
ease of use and performance. So let's analyze both of these
carefully.</para>
<para>With ease of use we can look at existing experience. The standard C++
objects that represent a system resource, such as std::iostream, are
noncopyable, so we know that C++ programmers must at least be experienced
with this design. Most C++ developers are also used to smart pointers such
as boost::shared_ptr, so we know they can at least adapt to a thread_ref
concept with little effort. So existing experience isn't going to lead us to
a choice.</para>
<para>The other thing we can look at is how difficult it is to use both
types for the six usage patterns above. If we find it overly difficult to
use a concept for any of the usage patterns there would be a good argument
for choosing the other design. So we'll code all six usage patterns using
both designs.</para>
<section id="thread.rationale_comparison.non-copyable.simple">
<title>1. Comparison: simple creation of a thread.</title>
<programlisting>
void foo()
{
thread thrd(&amp;bar);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="thread.rationale_comparison.non-copyable.joined">
<title>2. Comparison: creation of a thread that's later joined.</title>
<programlisting>
void foo()
{
thread thrd(&amp;bar);
thrd.join();
}
void foo()
{
thread_ref thrd =
create_thread(&amp;bar);thrd-&gt;join();
}
</programlisting>
</section>
<section id="thread.rationale_comparison.non-copyable.loop">
<title>3. Comparison: simple creation of several threads in a loop.</title>
<programlisting>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread thrd(&amp;bar);
}
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread_ref thrd = create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="thread.rationale_comparison.non-copyable.loop-join">
<title>4. Comparison: creation of several threads in a loop which are later joined.</title>
<programlisting>
void foo()
{
std::auto_ptr&lt;thread&gt; threads[NUM_THREADS];
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = std::auto_ptr&lt;thread&gt;(new thread(&amp;bar));
for (int i= 0; i&lt;NUM_THREADS;
++i)threads[i]-&gt;join();
}
void foo()
{
thread_ref threads[NUM_THREADS];
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = create_thread(&amp;bar);
for (int i= 0; i&lt;NUM_THREADS;
++i)threads[i]-&gt;join();
}
</programlisting>
</section>
<section id="thread.rationale_comparison.non-copyable.pass">
<title>5. Comparison: creation of a thread whose ownership is passed to another object/method.</title>
<programlisting>
void foo()
{
thread thrd* = new thread(&amp;bar);
manager.owns(thread);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager.owns(thrd);
}
</programlisting>
</section>
<section id="thread.rationale_comparison.non-copyable.shared">
<title>6. Comparison: creation of a thread whose ownership is shared
between multiple objects.</title>
<programlisting>
void foo()
{
boost::shared_ptr&lt;thread&gt; thrd(new thread(&amp;bar));
manager1.add(thrd);
manager2.add(thrd);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager1.add(thrd);
manager2.add(thrd);
}
</programlisting>
</section>
<para>This shows the usage patterns being nearly identical in complexity for
both designs. The only actual added complexity occurs because of the use of
operator new in
<link linkend="thread.rationale_comparison.non-copyable.loop-join">(4)</link>,
<link linkend="thread.rationale_comparison.non-copyable.pass">(5)</link>, and
<link linkend="thread.rationale_comparison.non-copyable.shared">(6)</link>;
and the use of std::auto_ptr and boost::shared_ptr in
<link linkend="thread.rationale_comparison.non-copyable.loop-join">(4)</link> and
<link linkend="thread.rationale_comparison.non-copyable.shared">(6)</link>
respectively. However, that's not really
much added complexity, and C++ programmers are used to using these idioms
anyway. Some may dislike the presence of operator new in user code, but
this can be eliminated by proper design of higher level concepts, such as
the boost::thread_group class that simplifies example
<link linkend="thread.rationale_comparison.non-copyable.loop-join">(4)</link>
down to:</para>
<programlisting>
void foo()
{
thread_group threads;
for (int i=0; i&lt;NUM_THREADS; ++i)
threads.create_thread(&amp;bar);
threads.join_all();
}
</programlisting>
<para>So ease of use is really a wash and not much help in picking a
design.</para>
<para>So what about performance? Looking at the above code examples,
we can analyze the theoretical impact to performance that both designs
have. For <link linkend="thread.rationale_comparison.non-copyable.simple">(1)</link>
we can see that platforms that don't have a ref-counted native
thread type (POSIX, for instance) will be impacted by a thread_ref
design. Even if the native thread type is ref-counted there may be an impact
if more state information has to be maintained for concepts foreign to the
native API, such as clean up stacks for Win32 implementations.
For <link linkend="thread.rationale_comparison.non-copyable.joined">(2)</link>
and <link linkend="thread.rationale_comparison.non-copyable.loop">(3)</link>
the performance impact will be identical to
<link linkend="thread.rationale_comparison.non-copyable.simple">(1)</link>.
For <link linkend="thread.rationale_comparison.non-copyable.loop-join">(4)</link>
things get a little more interesting and we find that theoretically at least
the thread_ref may perform faster since the thread design requires dynamic
memory allocation/deallocation. However, in practice there may be dynamic
allocation for the thread_ref design as well, it will just be hidden from
the user. As long as the implementation has to do dynamic allocations the
thread_ref loses again because of the reference management. For
<link linkend="thread.rationale_comparison.non-copyable.pass">(5)</link> we see
the same impact as we do for
<link linkend="thread.rationale_comparison.non-copyable.loop-join">(4)</link>.
For <link linkend="thread.rationale_comparison.non-copyable.shared">(6)</link>
we still have a possible impact to
the thread design because of dynamic allocation but thread_ref no longer
suffers because of its reference management, and in fact, theoretically at
least, the thread_ref may do a better job of managing the references. All of
this indicates that thread wins for
<link linkend="thread.rationale_comparison.non-copyable.simple">(1)</link>,
<link linkend="thread.rationale_comparison.non-copyable.joined">(2)</link> and
<link linkend="thread.rationale_comparison.non-copyable.loop">(3)</link>; with
<link linkend="thread.rationale_comparison.non-copyable.loop-join">(4)</link>
and <link linkend="thread.rationale_comparison.non-copyable.pass">(5)</link> the
winner depending on the implementation and the platform but with the thread design
probably having a better chance; and with
<link linkend="thread.rationale_comparison.non-copyable.shared">(6)</link>
it will again depend on the
implementation and platform but this time we favor thread_ref
slightly. Given all of this it's a narrow margin, but the thread design
prevails.</para>
<para>Given this analysis, and the fact that noncopyable objects for system
resources are the normal designs that C++ programmers are used to dealing
with, the &Boost.Thread; library has gone with a noncopyable design.</para>
</section>
<section id="thread.rationale.events">
<title>Rationale for not providing <emphasis>Event Variables</emphasis></title>
<para><emphasis>Event variables</emphasis> are simply far too
error-prone. <classname>boost::condition</classname> variables are a much safer
alternative. [Note that Graphical User Interface <emphasis>events</emphasis> are
a different concept, and are not what is being discussed here.]</para>
<para>Event variables were one of the first synchronization primitives. They
are still used today, for example, in the native Windows multithreading
API. Yet both respected computer science researchers and experienced
multithreading practitioners believe event variables are so inherently
error-prone that they should never be used, and thus should not be part of a
multithreading library.</para>
<para>Per Brinch Hansen &cite.Hansen73; analyzed event variables in some
detail, pointing out [emphasis his] that "<emphasis>event operations force
the programmer to be aware of the relative speeds of the sending and
receiving processes</emphasis>". His summary:</para>
<blockquote>
<para>We must therefore conclude that event variables of the previous type
are impractical for system design. <emphasis>The effect of an interaction
between two processes must be independent of the speed at which it is
carried out.</emphasis></para>
</blockquote>
<para>Experienced programmers using the Windows platform today report that
event variables are a continuing source of errors, even after previous bad
experiences caused them to be very careful in their use of event
variables. Overt problems can be avoided, for example, by teaming the event
variable with a mutex, but that may just convert a <link
linkend="thread.glossary.race-condition">race condition</link> into another
problem, such as excessive resource use. One of the most distressing aspects
of the experience reports is the claim that many defects are latent. That
is, the programs appear to work correctly, but contain hidden timing
dependencies which will cause them to fail when environmental factors or
usage patterns change, altering relative thread timings.</para>
<para>The decision to exclude event variables from &Boost.Thread; has been
surprising to some Windows programmers. They have written programs which
work using event variables, and wonder what the problem is. It seems similar
to the "goto considered harmful" controversy of 30 years ago. It isn't that
events, like gotos, can't be made to work, but rather that virtually all
programs using alternatives will be easier to write, debug, read, maintain,
and will be less likely to contain latent defects.</para>
<para>[Rationale provided by Beman Dawes]</para>
</section>
</section>

View File

@@ -1,492 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/read_write_mutex.hpp"
last-revision="$Date$">
<namespace name="boost">
<namespace name="read_write_scheduling_policy">
<enum name="read_write_scheduling_policy">
<enumvalue name="writer_priority" />
<enumvalue name="reader_priority" />
<enumvalue name="alternating_many_reads" />
<enumvalue name="alternating_single_read" />
<purpose>
<para>Specifies the
<link linkend="thread.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
to use when a set of threads try to obtain different types of
locks simultaneously.</para>
</purpose>
<description>
<para>The only clock type supported by &Boost.Thread; is
<code>TIME_UTC</code>. The epoch for <code>TIME_UTC</code>
is 1970-01-01 00:00:00.</para>
</description>
</enum>
</namespace>
<class name="read_write_mutex">
<purpose>
<para>The <classname>read_write_mutex</classname> class is a model of the
<link linkend="thread.concepts.ReadWriteMutex">ReadWriteMutex</link> concept.</para>
<note> Unfortunately it turned out that the current implementation of Read/Write Mutex has
some serious problems. So it was decided not to put this implementation into
release grade code. Also discussions on the mailing list led to the
conclusion that the current concepts need to be rethought. In particular
the schedulings <link linkend="thread.concepts.read-write-scheduling-policies.inter-class">
Inter-Class Scheduling Policies</link> are deemed unnecessary.
There seems to be common belief that a fair scheme suffices.
The following documentation has been retained however, to give
readers of this document the opportunity to study the original design.
</note>
</purpose>
<description>
<para>The <classname>read_write_mutex</classname> class is a model of the
<link linkend="thread.concepts.ReadWriteMutex">ReadWriteMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>try_read_write_mutex</classname> and <classname>timed_read_write_mutex</classname>.</para>
<para>The <classname>read_write_mutex</classname> class supplies the following typedefs,
which <link linkend="thread.concepts.read-write-lock-models">model</link>
the specified locking strategies:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_read_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedReadWriteLock">ScopedReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_read_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>read_write_mutex</classname> class uses an
<link linkend="thread.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>read_write_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
This strategy allows implementations to be as efficient as possible
on any given platform. It is, however, recommended that
implementations include debugging support to detect misuse when
<code>NDEBUG</code> is not defined.</para>
<para>Like all
<link linkend="thread.concepts.read-write-mutex-models">read/write mutex models</link>
in &Boost.Thread;, <classname>read_write_mutex</classname> has two types of
<link linkend="thread.concepts.read-write-scheduling-policies">scheduling policies</link>, an
<link linkend="thread.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
between threads trying to obtain different types of locks and an
<link linkend="thread.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link>
between threads trying to obtain the same type of lock.
The <classname>read_write_mutex</classname> class allows the
programmer to choose what
<link linkend="thread.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
will be used; however, like all read/write mutex models,
<classname>read_write_mutex</classname> leaves the
<link linkend="thread.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link> as
<link linkend="thread.concepts.read-write-locking-strategies.unspecified">Unspecified</link>.
</para>
<note>Self-deadlock is virtually guaranteed if a thread tries to
lock the same <classname>read_write_mutex</classname> multiple times
unless all locks are read-locks (but see below)</note>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_read_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_read_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<parameter name="count">
<paramtype>boost::read_write_scheduling_policy</paramtype>
</parameter>
<effects>Constructs a <classname>read_write_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>read_write_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="try_read_write_mutex">
<purpose>
<para>The <classname>try_read_write_mutex</classname> class is a model of the
<link linkend="thread.concepts.TryReadWriteMutex">TryReadWriteMutex</link> concept.</para>
<note> Unfortunately it turned out that the current implementation of Read/Write Mutex has
some serious problems. So it was decided not to put this implementation into
release grade code. Also discussions on the mailing list led to the
conclusion that the current concepts need to be rethought. In particular
the schedulings <link linkend="thread.concepts.read-write-scheduling-policies.inter-class">
Inter-Class Scheduling Policies</link> are deemed unnecessary.
There seems to be common belief that a fair scheme suffices.
The following documentation has been retained however, to give
readers of this document the opportunity to study the original design.
</note>
</purpose>
<description>
<para>The <classname>try_read_write_mutex</classname> class is a model of the
<link linkend="thread.concepts.TryReadWriteMutex">TryReadWriteMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>read_write_mutex</classname> and <classname>timed_read_write_mutex</classname>.</para>
<para>The <classname>try_read_write_mutex</classname> class supplies the following typedefs,
which <link linkend="thread.concepts.read-write-lock-models">model</link>
the specified locking strategies:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_read_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedReadWriteLock">ScopedReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_try_read_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryReadWriteLock">ScopedTryReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_read_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_read_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
<row>
<entry>scoped_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>try_read_write_mutex</classname> class uses an
<link linkend="thread.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>try_read_write_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
This strategy allows implementations to be as efficient as possible
on any given platform. It is, however, recommended that
implementations include debugging support to detect misuse when
<code>NDEBUG</code> is not defined.</para>
<para>Like all
<link linkend="thread.concepts.read-write-mutex-models">read/write mutex models</link>
in &Boost.Thread;, <classname>try_read_write_mutex</classname> has two types of
<link linkend="thread.concepts.read-write-scheduling-policies">scheduling policies</link>, an
<link linkend="thread.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
between threads trying to obtain different types of locks and an
<link linkend="thread.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link>
between threads trying to obtain the same type of lock.
The <classname>try_read_write_mutex</classname> class allows the
programmer to choose what
<link linkend="thread.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
will be used; however, like all read/write mutex models,
<classname>try_read_write_mutex</classname> leaves the
<link linkend="thread.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link> as
<link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
</para>
<note>Self-deadlock is virtually guaranteed if a thread tries to
lock the same <classname>try_read_write_mutex</classname> multiple times
unless all locks are read-locks (but see below)</note>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_read_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_read_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_read_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_read_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<parameter name="count">
<paramtype>boost::read_write_scheduling_policy</paramtype>
</parameter>
<effects>Constructs a <classname>try_read_write_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>try_read_write_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="timed_read_write_mutex">
<purpose>
<para>The <classname>timed_read_write_mutex</classname> class is a model of the
<link linkend="thread.concepts.TimedReadWriteMutex">TimedReadWriteMutex</link> concept.</para>
<note> Unfortunately it turned out that the current implementation of Read/Write Mutex has
some serious problems. So it was decided not to put this implementation into
release grade code. Also discussions on the mailing list led to the
conclusion that the current concepts need to be rethought. In particular
the schedulings <link linkend="thread.concepts.read-write-scheduling-policies.inter-class">
Inter-Class Scheduling Policies</link> are deemed unnecessary.
There seems to be common belief that a fair scheme suffices.
The following documentation has been retained however, to give
readers of this document the opportunity to study the original design.
</note>
</purpose>
<description>
<para>The <classname>timed_read_write_mutex</classname> class is a model of the
<link linkend="thread.concepts.TimedReadWriteMutex">TimedReadWriteMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>read_write_mutex</classname> and <classname>try_read_write_mutex</classname>.</para>
<para>The <classname>timed_read_write_mutex</classname> class supplies the following typedefs,
which <link linkend="thread.concepts.read-write-lock-models">model</link>
the specified locking strategies:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_read_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedReadWriteLock">ScopedReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_try_read_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryReadWriteLock">ScopedTryReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_timed_read_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedTimedReadWriteLock">ScopedTimedReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_read_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_read_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
<row>
<entry>scoped_timed_read_lock</entry>
<entry><link linkend="thread.concepts.ScopedTimedLock">ScopedTimedLock</link></entry>
</row>
<row>
<entry>scoped_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
<row>
<entry>scoped_timed_write_lock</entry>
<entry><link linkend="thread.concepts.ScopedTimedLock">ScopedTimedLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>timed_read_write_mutex</classname> class uses an
<link linkend="thread.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>timed_read_write_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
This strategy allows implementations to be as efficient as possible
on any given platform. It is, however, recommended that
implementations include debugging support to detect misuse when
<code>NDEBUG</code> is not defined.</para>
<para>Like all
<link linkend="thread.concepts.read-write-mutex-models">read/write mutex models</link>
in &Boost.Thread;, <classname>timed_read_write_mutex</classname> has two types of
<link linkend="thread.concepts.read-write-scheduling-policies">scheduling policies</link>, an
<link linkend="thread.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
between threads trying to obtain different types of locks and an
<link linkend="thread.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link>
between threads trying to obtain the same type of lock.
The <classname>timed_read_write_mutex</classname> class allows the
programmer to choose what
<link linkend="thread.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
will be used; however, like all read/write mutex models,
<classname>timed_read_write_mutex</classname> leaves the
<link linkend="thread.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link> as
<link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
</para>
<note>Self-deadlock is virtually guaranteed if a thread tries to
lock the same <classname>timed_read_write_mutex</classname> multiple times
unless all locks are read-locks (but see below)</note>
</description>
<typedef name="scoped_read_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_read_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_read_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_read_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_read_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_read_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_write_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<parameter name="count">
<paramtype>boost::read_write_scheduling_policy</paramtype>
</parameter>
<effects>Constructs a <classname>timed_read_write_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>timed_read_write_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
</namespace>
</header>

View File

@@ -1,306 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/recursive_mutex.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="recursive_mutex">
<purpose>
<para>The <classname>recursive_mutex</classname> class is a model of the
<link linkend="thread.concepts.Mutex">Mutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>recursive_mutex</classname> class is a model of the
<link linkend="thread.concepts.Mutex">Mutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>recursive_try_mutex</classname> and <classname>recursive_timed_mutex</classname>.</para>
<para>For <link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics, see <classname>mutex</classname>,
<classname>try_mutex</classname>, and <classname>timed_mutex</classname>.
</para>
<para>The <classname>recursive_mutex</classname> class supplies the following typedef,
which models the specified locking strategy:
<table>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>The <classname>recursive_mutex</classname> class uses a
<link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking strategy, so attempts to recursively lock a
<classname>recursive_mutex</classname> object
succeed and an internal "lock count" is maintained.
Attempts to unlock a <classname>recursive_mutex</classname> object
by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.</para>
<para>Like all
<link linkend="thread.concepts.mutex-models">mutex models</link>
in &Boost.Thread;, <classname>recursive_mutex</classname> leaves the
<link linkend="thread.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>recursive_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>recursive_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="recursive_try_mutex">
<purpose>
<para>The <classname>recursive_try_mutex</classname> class is a model of the
<link linkend="thread.concepts.TryMutex">TryMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>recursive_try_mutex</classname> class is a model of the
<link linkend="thread.concepts.TryMutex">TryMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>recursive_mutex</classname> and <classname>recursive_timed_mutex</classname>.</para>
<para>For <link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics, see <classname>mutex</classname>,
<classname>try_mutex</classname>, and <classname>timed_mutex</classname>.
</para>
<para>The <classname>recursive_try_mutex</classname> class supplies the following typedefs,
which model the specified locking strategies:
<table>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>The <classname>recursive_try_mutex</classname> class uses a
<link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking strategy, so attempts to recursively lock a
<classname>recursive_try_mutex</classname> object
succeed and an internal "lock count" is maintained.
Attempts to unlock a <classname>recursive_mutex</classname> object
by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.</para>
<para>Like all
<link linkend="thread.concepts.mutex-models">mutex models</link>
in &Boost.Thread;, <classname>recursive_try_mutex</classname> leaves the
<link linkend="thread.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>recursive_try_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>recursive_try_mutex</classname> object.
</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="recursive_timed_mutex">
<purpose>
<para>The <classname>recursive_timed_mutex</classname> class is a model of the
<link linkend="thread.concepts.TimedMutex">TimedMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>recursive_timed_mutex</classname> class is a model of the
<link linkend="thread.concepts.TimedMutex">TimedMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>recursive_mutex</classname> and <classname>recursive_try_mutex</classname>.</para>
<para>For <link linkend="thread.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics, see <classname>mutex</classname>,
<classname>try_mutex</classname>, and <classname>timed_mutex</classname>.
</para>
<para>The <classname>recursive_timed_mutex</classname> class supplies the following typedefs,
which model the specified locking strategies:
<table>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="thread.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="thread.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
<row>
<entry>scoped_timed_lock</entry>
<entry><link linkend="thread.concepts.ScopedTimedLock">ScopedTimedLock</link></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>The <classname>recursive_timed_mutex</classname> class uses a
<link linkend="thread.concepts.recursive-locking-strategy">Recursive</link>
locking strategy, so attempts to recursively lock a
<classname>recursive_timed_mutex</classname> object
succeed and an internal "lock count" is maintained.
Attempts to unlock a <classname>recursive_mutex</classname> object
by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.</para>
<para>Like all
<link linkend="thread.concepts.mutex-models">mutex models</link>
in &Boost.Thread;, <classname>recursive_timed_mutex</classname> leaves the
<link linkend="thread.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="thread.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>recursive_timed_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>recursive_timed_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
</namespace>
</header>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, recursive_mutex</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">recursive_mutex<br>
recursive_try_mutex<br>
recursive_timed_mutex</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#recursive_mutex Synopsis">Class recursive_mutex Synopsis</a><br>
<a href="#recursive_mutex Members">Class recursive_mutex Members</a><br>
<a href="#recursive_try_mutex Synopsis">Class recursive_try_mutex Synopsis</a><br>
<a href="#recursive_try_mutex Members">Class recursive_try_mutex Members</a><br>
<a href="#recursive_timed_mutex Synopsis">Class recursive_timed_mutex Synopsis</a><br>
<a href="#recursive_timed_mutex Members">Class recursive_timed_mutex Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and
<code>recursive_timed_mutex</code> classes define full featured models of the
<a href="mutex_concept.html#Mutex">Mutex</a>,
<a href="mutex_concept.html#TryMutex">TryMutex</a> and
<a href="mutex_concept.html#TimedMutex">TimedMutex</a> concepts with recursive locking
semantics. These types should be used to synchronize access to shared resources
when recursive locking by a single thread is likely to occur. A good example for this
is when a class supplies "internal synchronization" to ensure
<a href="definitions.html#Thread-safe">thread-safety</a> and a function of the class
may have to call other functions of the class which also attempt to lock the mutex.
For recursive locking mechanics, see <a href="mutex.html">mutexes</a>.
<p>Each class supplies one or more typedefs for lock types which model matching
lock concepts. For the best possible performance you should use the mutex class that
supports the minimum set of lock types that you need.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Mutex Class</b></td>
<td><b>Lock name</b></td>
<td><b>Implementation defined Lock Type</b></td>
<td><b>Lock Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#recursive_mutex Synopsis"><code>recursive_mutex</code></a></td>
<td valign="middle"><code>scoped_lock</code></td>
<td valign="middle"><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;recursive_mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a></td>
</tr>
<tr>
<td valign="top"><code><a href="#recursive_try_mutex Synopsis">recursive_try_mutex</a></code></td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock</code></td>
<td valign="middle"><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;recursive_try_mutex&gt;<br>
</code></a><code><a href="scoped_try_lock.html">detail::thread::scoped_try_lock&lt;recursive_try_mutex&gt;</a></code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a></td>
</tr>
<tr>
<td valign="top"><code><a href="#recursive_timed_mutex Synopsis">recursive_timed_mutex</a></code> </td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock<br>
scoped_timed_lock</code></td>
<td valign="middle"><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;recursive_timed_mutex&gt;</code></a><br>
<a href="scoped_try_lock.html"><code>detail::thread::scoped_try_lock&lt;recursive_timed_mutex&gt;</code></a><br>
<a href="scoped_timed_lock.html"><code>detail::thread::scoped_timed_lock&lt;recursive_timed_mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a><br>
<a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a></td>
</tr>
</table>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and
<code>recursive_timed_mutex</code> employ a <code>Recursive</code>
<a href="mutex_concept.html#LockingStrategies">locking strategy</a>, so attempts to
recursively lock them succeed and an internal "lock count" is maintained. Attempts
to unlock them by a thread that does not own a lock on them will result in a
<a href="lock_error.html">lock_error</a> exception being thrown.</p>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and
<code>recursive_timed_mutex</code> leave the
<a href="mutex_concept.html#SchedulingPolicies">scheduling policy</a> as
<code>Unspecified</code>. Programmers should assume that threads waiting for a lock on
objects of these types acquire the lock in a random order, even though the specific
behavior for a given platform may be different.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a>
</pre>
<h2>Class <a name="recursive_mutex Synopsis"> recursive_mutex Synopsis</a></h2>
<hr>
<pre>
namespace boost
{
class recursive_mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class recursive_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
recursive_mutex();
~recursive_mutex();
};
}
</pre>
<h2>Class <a name="recursive_mutex Members">recursive_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
recursive_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~recursive_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash..</p>
<hr>
<h2>
Class <a name="recursive_try_mutex Synopsis">recursive_try_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class recursive_try_mutex : private boost::noncopyable // Exposition only.
// Class recursive_try_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
recursive_try_mutex();
~recursive_try_mutex();
};
}
</pre>
<h2>Class <a name="recursive_try_mutex Members">recursive_try_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
recursive_try_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~recursive_try_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash..</p>
<hr>
<h2>
Class <a name="recursive_timed_mutex Synopsis">recursive_timed_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class recursive_timed_mutex : private boost::noncopyable // Exposition only.
// Class recursive_timed_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_timed_lock;
recursive_timed_mutex();
~recursive_timed_mutex();
};
}
</pre>
<h2>
Class <a name="recursive_timed_mutex Members">recursive_timed_mutex Members</a>
</h2>
<hr>
<h3>Constructor</h3>
<pre>
recursive_timed_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~recursive_timed_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash..</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
class counter
{
public:
counter() : count(0) { }
int add(int val) {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
count += val;
return count;
}
int increment() {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
return add(1);
}
private:
boost::recursive_mutex mutex;
int count;
};
counter c;
void change_count(void*)
{
std::cout &lt;&lt; &quot;count == &quot; &lt;&lt; c.increment() &lt;&lt; std::endl;
}
int main(int, char*[])
{
const int num_threads=4;
boost::thread_group threads;
for (int i=0; i &lt; num_threads; ++i)
threads.create_thread(&amp;change_count, 0);
threads.join_all();
return 0;
}
</pre>
<p>The output is:</p>
<pre>
count == 1
count == 2
count == 3
count == 4
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<library-reference id="thread.reference"
last-revision="$Date$"
xmlns:xi="http://www.w3.org/2001/XInclude">
<xi:include href="barrier-ref.xml"/>
<xi:include href="condition-ref.xml"/>
<xi:include href="exceptions-ref.xml"/>
<xi:include href="mutex-ref.xml"/>
<xi:include href="once-ref.xml"/>
<xi:include href="recursive_mutex-ref.xml"/>
<!--
The read_write_mutex is held back from release, since the
implementation suffers from a serious, yet unresolved bug.
The implementation is likely to appear in a reworked
form in the next release.
-->
<xi:include href="read_write_mutex-ref.xml"/>
<xi:include href="thread-ref.xml"/>
<xi:include href="tss-ref.xml"/>
<xi:include href="xtime-ref.xml"/>
</library-reference>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<section id="thread.release_notes" last-revision="$Date$">
<title>Release Notes</title>
<section id="thread.release_notes.boost_1_34_0">
<title>Boost 1.34.0</title>
<section id="thread.release_notes.boost_1_34_0.change_log.maintainance">
<title>New team of maintainers</title>
<para>
Since the original author William E. Kempf no longer is available to
maintain the &Boost.Thread; library, a new team has been formed
in an attempt to continue the work on &Boost.Thread;.
Fortunately William E. Kempf has given
<ulink url="http://lists.boost.org/Archives/boost/2006/09/110143.php">
permission </ulink>
to use his work under the boost license.
</para>
<para>
The team currently consists of
<itemizedlist>
<listitem>
Anthony Williams, for the Win32 platform,
</listitem>
<listitem>
Roland Schwarz, for the linux platform, and various "housekeeping" tasks.
</listitem>
</itemizedlist>
Volunteers for other platforms are welcome!
</para>
<para>
As the &Boost.Thread; was kind of orphaned over the last release, this release
attempts to fix the known bugs. Upcoming releases will bring in new things.
</para>
</section>
<section id="thread.release_notes.boost_1_34_0.change_log.read_write_mutex">
<title>read_write_mutex still broken</title>
<para>
<note>
It has been decided not to release the Read/Write Mutex, since the current
implementation suffers from a serious bug. The documentation of the concepts
has been included though, giving the interested reader an opportunity to study the
original concepts. Please refer to the following links if you are interested
which problems led to the decision to held back this mutex type.The issue
has been discovered before 1.33 was released and the code has
been omitted from that release. A reworked mutex is expected to appear in 1.35.
Also see:
<ulink url="http://lists.boost.org/Archives/boost/2005/08/92307.php">
read_write_mutex bug</ulink>
and
<ulink url="http://lists.boost.org/Archives/boost/2005/09/93180.php">
read_write_mutex fundamentally broken in 1.33</ulink>
</note>
</para>
</section>
</section>
<section id="thread.release_notes.boost_1_32_0">
<title>Boost 1.32.0</title>
<section id="thread.release_notes.boost_1_32_0.change_log.documentation">
<title>Documentation converted to BoostBook</title>
<para>The documentation was converted to BoostBook format,
and a number of errors and inconsistencies were
fixed in the process.
Since this was a fairly large task, there are likely to be
more errors and inconsistencies remaining. If you find any,
please report them!</para>
</section>
<section id="thread.release_notes.boost_1_32_0.change_log.static_link">
<title>Statically-link build option added</title>
<para>The option to link &Boost.Thread; as a static
library has been added (with some limitations on Win32 platforms).
This feature was originally removed from an earlier version
of Boost because <classname>boost::thread_specific_ptr</classname>
required that &Boost.Thread; be dynamically linked in order
for its cleanup functionality to work on Win32 platforms.
Because this limitation never applied to non-Win32 platforms,
because significant progress has been made in removing
the limitation on Win32 platforms (many thanks to
Aaron LaFramboise and Roland Scwarz!), and because the lack
of static linking is one of the most common complaints of
&Boost.Thread; users, this decision was reversed.</para>
<para>On non-Win32 platforms:
To choose the dynamically linked version of &Boost.Thread;
using Boost's auto-linking feature, #define BOOST_THREAD_USE_DLL;
to choose the statically linked version,
#define BOOST_THREAD_USE_LIB.
If neither symbols is #defined, the default will be chosen.
Currently the default is the statically linked version.</para>
<para>On Win32 platforms using VC++:
Use the same #defines as for non-Win32 platforms
(BOOST_THREAD_USE_DLL and BOOST_THREAD_USE_LIB).
If neither is #defined, the default will be chosen.
Currently the default is the statically linked version
if the VC++ run-time library is set to
"Multi-threaded" or "Multi-threaded Debug", and
the dynamically linked version
if the VC++ run-time library is set to
"Multi-threaded DLL" or "Multi-threaded Debug DLL".</para>
<para>On Win32 platforms using compilers other than VC++:
Use the same #defines as for non-Win32 platforms
(BOOST_THREAD_USE_DLL and BOOST_THREAD_USE_LIB).
If neither is #defined, the default will be chosen.
Currently the default is the dynamically linked version
because it has not yet been possible to implement automatic
tss cleanup in the statically linked version for compilers
other than VC++, although it is hoped that this will be
possible in a future version of &Boost.Thread;.
Note for advanced users: &Boost.Thread; provides several "hook"
functions to allow users to experiment with the statically
linked version on Win32 with compilers other than VC++.
These functions are on_process_enter(), on_process_exit(),
on_thread_enter(), and on_thread_exit(), and are defined
in tls_hooks.cpp. See the comments in that file for more
information.</para>
</section>
<section id="thread.release_notes.boost_1_32_0.change_log.barrier">
<title>Barrier functionality added</title>
<para>A new class, <classname>boost::barrier</classname>, was added.</para>
</section>
<section id="thread.release_notes.boost_1_32_0.change_log.read_write_mutex">
<title>Read/write mutex functionality added</title>
<para>New classes,
<classname>boost::read_write_mutex</classname>,
<classname>boost::try_read_write_mutex</classname>, and
<classname>boost::timed_read_write_mutex</classname>
were added.
<note>Since the read/write mutex and related classes are new,
both interface and implementation are liable to change
in future releases of &Boost.Thread;.
The lock concepts and lock promotion in particular are
still under discussion and very likely to change.</note>
</para>
</section>
<section id="thread.release_notes.boost_1_32_0.change_log.thread_specific_ptr">
<title>Thread-specific pointer functionality changed</title>
<para>The <classname>boost::thread_specific_ptr</classname>
constructor now takes an optional pointer to a cleanup function that
is called to release the thread-specific data that is being pointed
to by <classname>boost::thread_specific_ptr</classname> objects.</para>
<para>Fixed: the number of available thread-specific storage "slots"
is too small on some platforms.</para>
<para>Fixed: <functionname>thread_specific_ptr::reset()</functionname>
doesn't check error returned by <functionname>tss::set()</functionname>
(the <functionname>tss::set()</functionname> function now throws
if it fails instead of returning an error code).</para>
<para>Fixed: calling
<functionname>boost::thread_specific_ptr::reset()</functionname> or
<functionname>boost::thread_specific_ptr::release()</functionname>
causes double-delete: once when
<functionname>boost::thread_specific_ptr::reset()</functionname> or
<functionname>boost::thread_specific_ptr::release()</functionname>
is called and once when
<functionname>boost::thread_specific_ptr::~thread_specific_ptr()</functionname>
is called.</para>
</section>
<section id="thread.release_notes.boost_1_32_0.change_log.mutex">
<title>Mutex implementation changed for Win32</title>
<para>On Win32, <classname>boost::mutex</classname>,
<classname>boost::try_mutex</classname>, <classname>boost::recursive_mutex</classname>,
and <classname>boost::recursive_try_mutex</classname> now use a Win32 critical section
whenever possible; otherwise they use a Win32 mutex. As before,
<classname>boost::timed_mutex</classname> and
<classname>boost::recursive_timed_mutex</classname> use a Win32 mutex.</para>
</section>
<section id="thread.release_notes.boost_1_32_0.change_log.wince">
<title>Windows CE support improved</title>
<para>Minor changes were made to make Boost.Thread work on Windows CE.</para>
</section>
</section>
</section>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, atomic_t</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">atomic_t</h2>
</td>
</tr>
</table>
<hr>
<h2>Header</h2>
<p>The <tt>atomic_t</tt> class defines an "atomic integer" type. This class should be used
to perform thread safe operations on an integral type with out the overhead of locks. Only
a limited set of integer operations are available with an <tt>atomic_t</tt> instance.</p>
<pre>
#include &lt;boost/thread/atomic.hpp&gt;
</pre>
<h2>Public Interface</h2>
<pre>
class atomic_t
{
public:
typedef <b>implementation defined</b> value_type;
explicit atomic_t(value_type val=0);
};
atomic_t::value_type read(const atomic_t&amp; x);
atomic_t::value_type increment(atomic_t&amp; x);
atomic_t::value_type decrement(atomic_t&amp; x);
atomic_t::value_type swap(atomic_t&amp; x, atomic_t::value_type y);
atomic_t::value_type compare_swap(atomic_t&amp; x, atomic_t::value_type y, atomic_t::value_type z);
</pre>
<h3>Constructor</h3>
<pre>
atomic_t(atomic_t::value_type val=0);
</pre>
<p>Constructs an <tt>atomic_t</tt> and sets its value to <tt>val</tt>.</p>
<h3>read</h3>
<pre>
atomic_t::value_type read(const atomic_t&amp; x);
</pre>
<p>Gets the current value of <tt>x</tt>.</p>
<h3>increment</h3>
<pre>
atomic_t::value_type increment(atomic_t&amp; x);
</pre>
<p>Increments <tt>x</tt> and returns a value <tt>&lt; 0</tt> if the result is less than 0,
<tt>&gt; 0</tt> if the result is greater than 0 and <tt>== 0</tt> if the result is equal to
0.</p>
<h3>decrement</h3>
<pre>
atomic_t::value_type decrement(atomic_t&amp; x);
</pre>
<p>Decrements <tt>x</tt> and returns a value <tt>&lt; 0</tt> if the result is less than 0,
<tt>&gt; 0</tt> if the result is greater than 0 and <tt>== 0</tt> if the result is equal to
0.</p>
<h3>swap</h3>
<pre>
atomic_t::value_type swap(atomic_t&amp; x, atomic_t::value_type y);
</pre>
<p>Assigns the value of <tt>y</tt> to <tt>x</tt> and returns the value of <tt>x</tt> prior
to the swap.</p>
<h3>compare_swap</h3>
<pre>
atomic_t::value_type compare_swap(atomic_t&amp; x, atomic_t::value_type y, atomic_t::value_type z);
</pre>
<p>Compares the value of <tt>z</tt> to the value of <tt>x</tt> and if equal sets the value of
<tt>x</tt> to the value of <tt>y</tt> and returns the value of <tt>x</tt> prior to the swap.</p>
<h2>Example Usage</h2>
<pre>
#include &lt;boost/thread/atomic.hpp&gt;
#include &lt;boost/test/test_tools.hpp&gt;
int test_main(int, char*[])
{
boost::atomic_t a;
BOOST_TEST_VERIFY(boost::read(a) == 0);
BOOST_TEST_VERIFY(boost::increment(a) &gt; 0);
BOOST_TEST_VERIFY(boost::decrement(a) == 0);
BOOST_TEST_VERIFY(boost::swap(a, 1) == 0);
BOOST_TEST_VERIFY(boost::swap(a, 2, 0) == 1);
BOOST_TEST_VERIFY(boost::read(a) == 1);
}
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->06 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34352" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, scoped_lock</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">scoped_lock</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>This class template defines a generic lock type which meets the
<a href="lock_concept.html#ScopedLock">ScopedLock</a> requirements. The
<a href="mutex.html">mutex</a>, <a href="mutex.html">try_mutex</a>,
<a href="mutex.html">timed_mutex</a>, <a href="recursive_mutex.html">recursive_mutex</a>,
<a href="recursive_mutex.html">recursive_try_mutex</a> and
<a href="recursive_mutex.html">recursive_timed_mutex</a> classes all use this template
to define their <code>scoped_lock</code> types.</p>
<p>Like all the <b>Boost.Threads</b> <a href="lock_concept.html">lock models</a>,
<code>scoped_lock</code> objects are meant to be short-lived. Objects of the class
are not <a href="definitions.html#thread-safe">thread-safe</a>, and so should not be
shared between threads.</p>
<p>Class <code> scoped_lock</code> follows the &quot;resource acquisition is
initialization&quot; idiom <a href="bibliography.html#Stroustrup-00">[Stroustrup
00 14.4.1]</a> and is a realization of the &quot;Scoped Locking Pattern&quot;
<a href="bibliography.html#Schmidt-00">[Schmidt-00]</a>. Thus the usage is to let the
constructor do the locking, and then let the destructor do the unlocking automatically at
the end of the enclosing scope. The lock() and unlock() members are usually not
explicitly called, but are provided to allow for complex overlapping locks of multiple
mutexes.</p>
<p>The type used to instantiate the class must meet the
<a href="mutex_concept.html#Mutex">Mutex</a> requirements.</p>
<p>Although this class is an implementation detail, it is publicly documented here because
of its importance.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/detail/lock.hpp">&lt;boost/thread/detail/lock.hpp&gt;</a>
<i>This header is usually not included directly by programmers
because it is supplied by <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a> or
<a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a></i>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost { namespace detail { namespace thread {
template &lt;typename Mutex&gt;
class scoped_lock : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class scoped_lock meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef Mutex mutex_type;
explicit scoped_lock(Mutex&amp; mx, bool initially_locked=true);
~scoped_lock();
void lock();
void unlock();
operator const void*() const;
bool locked() const;
};
} // namespace thread
} // namespace detail
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
explicit scoped_lock(Mutex&amp; mx, bool initially_locked=true);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
If <code>initially_locked</code> is <code>true,</code> calls <code>lock()</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~scoped_lock();
</pre>
<p><b>Effects:</b> If <code> locked()</code>, calls <code>unlock()</code>. Destroys
<code>*this</code>.</p>
<hr>
<h3>lock</h3>
<pre>
void lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5">
<tr>
<td><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td><i>Effect if associated mutex is already locked by the current thread</i></td>
</tr>
<tr>
<td>Recursive</td>
<td>As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td>Checked</td>
<td>Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td>Unchecked</td>
<td>Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is already locked by some other thread, places the
current thread in the <a href="definitions.html#State">Blocked</a> state until
the associated mutex is unlocked, after which the current thread is placed in
the <a href="definitions.html#State">Ready</a> state, eventually to be returned
to the <a href="definitions.html#State">Running</a> state.
<p><b>Postcondition:</b> locked()
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>unlock</h3>
<pre>
void unlock();
</pre>
<p><b>Effects: </b>Unlocks the associated mutex.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>!locked()</code>.</p>
<hr>
<h3>const void* Conversion</h3>
<pre>
operator const void*() const;
</pre>
<p><b>Returns:</b> If the associated mutex is currently locked, a value convertible to
<code>true</code>, else a value convertible to <code>false</code>.</p>
<p><b>Rationale:</b> A <code>const void*</code> conversion is considered safer than a
conversion to <code>bool</code>.</p>
<hr>
<h3>locked</h3>
<pre>
bool locked() const;
</pre>
<p><b>Returns:</b> <code>this-&gt;operator const void*() != 0</code>.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<p>See the example given in the documentation for the <a href="mutex.html">mutex</a>
class.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, scoped_timed_lock</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">scoped_timed_lock</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>This class template defines a generic lock type which meets the
<a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a> requirements. The
<a href="mutex.html">timed_mutex</a> and
<a href="recursive_mutex.html">recursive_timed_mutex</a> classes use this template to
define their <code>scoped_timed_lock</code> types.</p>
<p>Like all the <b>Boost.Threads</b> <a href="lock_concept.html">lock models</a>,
<code>scoped_timed_lock</code> objects are meant to be short-lived. Objects of the
class are not <a href="definitions.html#thread-safe">thread-safe</a>, and so should
not be shared between threads.</p>
<p>Class <code>scoped_timed_lock</code> follows the &quot;resource acquisition is
initialization&quot; idiom <a href="bibliography.html#Stroustrup-00">[Stroustrup
00 14.4.1]</a> and is a realization of the &quot;Scoped Locking Pattern&quot;
<a href="bibliography.html#Schmidt-00">[Schmidt-00]</a>. Thus the usage is to let the
constructor do the locking, and then let the destructor do the unlocking automatically
at the end of the enclosing scope. The lock() and unlock() members are usually not
explicitly called, but are provided to allow for complex overlapping locks of multiple
mutexes.</p>
<p>The type used to instantiate the class must meet the
<a href="mutex_concept.html#TimedMutex">TimedMutex</a> requirements.</p>
<p>Although this class is an implementation detail, it is publicly documented here because
of its importance.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/detail/lock.hpp">&lt;boost/thread/detail/lock.hpp&gt;</a>
<i>This header is usually not included directly by programmers
because it is supplied by <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a> or
<a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a></i>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost { namespace detail { namespace thread {
template &lt;typename TimedMutex&gt;
class scoped_timed_lock : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class scoped_timed_lock meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef TimedMutex mutex_type;
scoped_timed_lock(TimedMutex&amp; mx, const boost::xtime&amp; xt);
scoped_timed_lock(TimedMutex&amp; mx, bool initially_locked);
~scoped_timed_lock();
void lock();
bool timed_lock(const xtime&amp; xt);
void unlock();
operator const void*() const;
};
} // namespace thread
} // namesapce detail
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
scoped_timed_lock(TimedMutex&amp; mx, const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
Calls <code>timed_lock</code>( <code>xt</code>)</p>
<hr>
<pre>
scoped_timed_lock(TimedMutex&amp; mx, bool initially_locked);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
If <code>initially_locked</code> is <code>true</code>, calls <code>lock()</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~scoped_timed_lock();
</pre>
<p><b>Effects:</b> If <code> locked()</code>, calls <code>unlock()</code>. Destroys
<code>*this</code>.</p>
<hr>
<h3>lock</h3>
<pre>
void lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5">
<tr>
<td><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td><i>Effect if associated mutex is already locked by the current thread</i></td>
</tr>
<tr>
<td>Recursive</td>
<td>As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td>Checked</td>
<td>Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td>Unchecked</td>
<td>Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is already locked by some other thread, places the
current thread in the <a href="definitions.html#State">Blocked</a> state until
the associated mutex is unlocked, after which the current thread is placed in
the <a href="definitions.html#State">Ready</a> state, eventually to be returned
to the <a href="definitions.html#State">Running</a> state. Places the associated
mutex in the locked state.
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>timed_lock</h3>
<pre>
bool timed_lock(const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Effects:</b> Same as <code>lock()</code>, except that if xt is reached,
places the current thread in the <a href="definitions.html#State">Ready</a>
state without further ado.</p>
<p><b>Returns:</b> <code>locked()</code>.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>unlock</h3>
<pre>
void unlock();
</pre>
<p><b>Effects: </b>Unlocks the associated mutex.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>!locked()</code>.</p>
<hr>
<h3>const void* Conversion</h3>
<pre>
operator const void*() const;
</pre>
<p><b>Returns:</b> If the associated mutex is currently locked, a value convertible to
<code>true</code>, else a value convertible to <code>false</code>.</p>
<p><b>Rationale:</b> A <code>const void*</code> conversion is considered safer than a
conversion to <code>bool</code>.</p>
<hr>
<h3>locked</h3>
<pre>
bool locked() const;
</pre>
<p><b>Returns:</b> <code>this-&gt;operator const void*() != 0</code>.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include &lt;boost/thread/mutex.hpp&gt;
#include &lt;iostream&gt;
int main(int, char*[])
{
boost::timed_mutex mutex;
boost::xtime xt;
boost::get_xtime(&amp;xt, boost::TIME_UTC);
xt.sec += 1;
boost::mutex::scoped_timed_lock scope_timed_lock(mutex, xt);
if (scope_timed_lock.locked())
std::cout &lt;&lt; &quot;locked&quot; &lt;&lt; std::endl;
else
std::cout &lt;&lt; &quot;unlocked&quot; &lt;&lt; std::endl;
return 0;
}
</pre>
<p>The output is:</p>
<pre>
locked
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%B %d, %Y" startspan -->September 13, 2001<!--webbot bot="Timestamp" endspan i-checksum="37965" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, scoped_try_lock</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">scoped_try_lock</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>This class template defines a generic lock type which meets the
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a> requirements. The
<a href="mutex.html">try_mutex</a>, <a href="mutex.html">timed_mutex</a>,
<a href="recursive_mutex.html">recursive_try_mutex</a> and
<a href="recursive_mutex.html">recursive_timed_mutex</a> classes use this template
to define their <code>scoped_try_lock</code> types.</p>
<p>Like all the <b>Boost.Threads</b> <a href="lock_concept.html">lock models</a>,
<code>scoped_try_lock</code> objects are meant to be short-lived. Objects of the
class are not <a href="definitions.html#thread-safe">thread-safe</a>, and
so should not be shared between threads.</p>
<p>Class <code> scoped_try_lock</code> follows the &quot;resource acquisition is
initialization&quot; idiom <a href="bibliography.html#Stroustrup-00">[Stroustrup
00 14.4.1]</a> and is a realization of the &quot;Scoped Locking Pattern&quot;
<a href="bibliography.html#Schmidt-00">[Schmidt-00]</a>. Thus the usage is to let the
constructor do the locking, and then let the destructor do the unlocking automatically at
the end of the enclosing scope. The lock() and unlock() members are usually not
explicitly called, but are provided to allow for complex overlapping locks of multiple
mutexes.</p>
<p>Although this class is an implementation detail, it is publicly documented here because
of its importance.</p>
<p>The type used to instantiate the class must meet the <a href="mutex_concept.html#TryMutex">TryMutex</a> requirements.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/detail/lock.hpp">&lt;boost/thread/detail/lock.hpp&gt;</a>
<i>This header is usually not included directly by programmers
because it is supplied by <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a> or
<a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a></i>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost { namespace detail { namespace thread {
template &lt;typename TryMutex&gt;
class scoped_try_lock : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class scoped_try_lock meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef TryMutex mutex_type;
explicit scoped_try_lock(TryMutex&amp; mx);
scoped_try_lock(TryMutex&amp; mx, bool initially_locked);
~scoped_try_lock();
void lock();
bool try_lock();
void unlock();
operator const void*() const;
};
} // namespace thread
} // namespace detail
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructors</h3>
<pre>
explicit scoped_try_lock(TryMutex&amp; mx);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
Calls <code>try_lock()</code>.</p>
<hr>
<pre>
scoped_try_lock(TryMutex&amp; mx, bool initially_locked);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
If <code>initially_locked</code> is <code>true,</code> calls <code>lock()</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~scoped_try_lock();
</pre>
<p><b>Effects:</b> If <code>locked()</code>, calls <code>unlock()</code>. Destroys
<code>*this</code>.</p>
<hr>
<h3>lock</h3>
<pre>
void lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5" height="147">
<tr>
<td height="34"><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td height="34"><i>Effect if associated mutex is already locked by the
current thread</i></td>
</tr>
<tr>
<td height="19">Recursive</td>
<td height="19">As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td height="19">Checked</td>
<td height="19">Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td height="19">Unchecked</td>
<td height="19">Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is already locked by some other thread, places the
current thread in the <a href="definitions.html#State">Blocked</a> state until
the associated mutex is unlocked, after which the current thread is placed in
the <a href="definitions.html#State">Ready</a> state, eventually to be returned
to the <a href="definitions.html#State">Running</a> state. Places the associated
mutex in the locked state.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>try_lock</h3>
<pre>
bool try_lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5" height="147">
<tr>
<td height="34"><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td height="34"><i>Effect if associated mutex is already locked by the
current thread</i></td>
</tr>
<tr>
<td height="19">Recursive</td>
<td height="19">As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td height="19">Checked</td>
<td height="19">Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td height="19">Unspecified</td>
<td height="19">Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is not already locked by some other thread, locks the
associated mutex and returns true, else returns false.</p>
<p><b>Returns:</b> See effects.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>unlock</h3>
<pre>
void unlock();
</pre>
<p><b>Effects: </b>Unlocks the associated mutex.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>!locked()</code>.</p>
<hr>
<h3>const void* Conversion</h3>
<pre>
operator const void*() const;
</pre>
<p><b>Returns:</b> If the associated mutex is currently locked, a value convertible to
<code>true</code>, else a value convertible to <code>false</code>.</p>
<p><b>Rationale:</b> A <code>const void*</code> conversion is considered safer
than a conversion to <code>bool</code>.</p>
<hr>
<h3>locked</h3>
<pre>
bool locked() const;
</pre>
<p><b>Returns:</b> <code>this-&gt;operator const void*() != 0</code>.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
#include &lt;iostream&gt;
int main(int, char*[])
{
boost::mutex mutex;
boost::mutex::try_lock lock(mutex);
if (lock)
std::cout &lt;&lt; &quot;locked&quot; &lt;&lt; std::endl;
else
std::cout &lt;&lt; &quot;unlocked&quot; &lt;&lt; std::endl;
return 0;
}
</pre>
<p>The output is:</p>
<pre>
locked
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, semaphore</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">semaphore</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt>semaphore</tt> class defines a classic synchronization primitive invented by the
Dutch computer scientist Edsger W. Dijkstra. A semaphore manages an internal counter. This
counter never goes below zero, or above a specified maximum value. When calling
<tt>semaphore::down</tt> the calling thread will block until the value is non-zero and then
decrement the value in a single atomic operation. When calling <tt>semaphore::up</tt> the
calling thread will increment the value in a single atomic operation, failing if the value has
already reached the specified maximum.</p>
<p><b>Rationale:</b> The semaphore is the simplest synchronization primitive available and is generally the
primitive used to build other synchronization concepts at some level of implementation. For this
reason <b>Boost.Threads</b> defines the <tt>semaphore</tt> type in the classic form. This simplifies
usage and implementation, but it means that the interface is not as safe as other <b>Boost.Threads</b>
interfaces.</p>
<p><b><a name="Danger">Danger</a>:</b> Unlike the <A href="mutex_concept.html">mutex models</a> supplied by <b>Boost.Threads,</b>
there is no <A href="lock_concept.html">lock_concept</a> for the semaphore to help ensure proper
usage. Great care must be taken when using a <tt>semaphore</tt> object to ensure
<a href="definitions.html#Deadlock"> deadlock</a> or <a href="definitions.html#Race condition">race conditions</a> do not occur.&nbsp;</p>
<p>The dangers are spelled out by <a href="bibliography.html#Andrews-83">[Andrews-83]</a>
(function names updated, see historical note below):&nbsp;</p>
<blockquote>
<p>Although semaphores can be used to program almost any kind of synchronization,
<b>down()</b> and <b>up()</b> are rather unstructured primitives, and so it is easy to err when using them. Execution of each critical section must begin with a
<b>down()</b> and end with a <b>up()</b> (on the same semaphore). Omitting a <b>down()</b>
or <b>up()</b>, or accidentally coding a <b>down()</b> on one semaphore and a <b>up()</b>
on another can have disastrous effects, since mutually exclusive execution would no longer be ensured. Also, when using semaphores, a programmer can forget to include in critical sections all statements that reference shared objects. This, too, could destroy the mutual exclusion required within critical sections. A second difficulty with using semaphores is that both condition synchronization and mutual exclusion are programmed using the same pair of primitives. This makes it difficult to identify the purpose of a given
<b>down()</b> or <b>up()</b> operation without looking at the other operations on the corresponding semaphore. Since mutual exclusion and condition synchronization are distinct concepts, they should have distinct notations.</p>
</blockquote>
<p><b>Historical note: </b>Dijkstra's original name for <b>down()</b> was <b>P</b>
(short for the Dutch &quot;passeren&quot;, &quot;to pass&quot;), and for <b>up()</b>
was <b>V</b> (short for the Dutch &quot;vrygeven&quot;, &quot;to release&quot;).</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/semaphore.hpp">&lt;boost/thread/semaphore.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
{
class semaphore : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class semaphore meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
explicit semaphore(unsigned count=0, unsigned max=0);
~semaphore();
bool up(unsigned count=1, unsigned* prev=0);
void down();
bool down(const xtime&amp; xt);
private:
unsigned m_count; <i>exposition only [ISO 17.3.2.3/2]
</i> unsigned m_max; <i>exposition only [ISO 17.3.2.3/2]</i>
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
explicit semaphore(unsigned count=0, unsigned max=0);
</pre>
<p><b>Effects:</b> As if:</p>
<p><code>&nbsp;&nbsp;&nbsp;&nbsp; m_count = count;<br>
&nbsp;&nbsp;&nbsp;&nbsp; m_max = (max == 0 ? std::numeric_limits&lt;unsigned&gt;::max()
? max );</code></p>
<hr>
<h3>Destructor</h3>
<pre>
~semaphore();
</pre>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<hr>
<h3>up</h3>
<pre>
bool up(unsigned count=1, unsigned* prev=0);
</pre>
<p><b>Effects:</b> As if:</p>
<p><code>&nbsp;&nbsp;&nbsp; unsigned ct;<br>
&nbsp;&nbsp;&nbsp; bool ret;<br>
&nbsp;&nbsp;&nbsp; { // as a single atomic operation:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ct = m_count;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (m_count == m_max) ret =
false;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; else<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; {<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret =
true;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ++m_count;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>
&nbsp;&nbsp;&nbsp; }<br>
&nbsp;&nbsp;&nbsp; if (prev) *prev = m_count;<br>
&nbsp;&nbsp;&nbsp; return ret;</code></p>
<hr>
<h3>down</h3>
<pre>
void down();
</pre>
<p><b>Effects:</b> If <code>m_count == 0</code>, places the current thread in
the <a href="definitions.html#State">blocked</a> state until <code>m_count != 0</code>.
Finally, <code>--m_count</code>.<code>&nbsp;</code></p>
<hr>
<pre>
bool down(const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Effects:</b> If <code>m_count == 0</code>, places the current thread in
the <a href="definitions.html#State">blocked</a> state until <code>m_count != 0</code>
or <code>xt</code> is reached. Finally, <code>--m_count</code>.<code>&nbsp;</code></p>
<p><b>Returns:</b> If xt was reached, true, else false.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/semaphore.hpp">&lt;boost/thread/semaphore.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
int global_data = 0;
boost::semaphore global_semaphore(1);
void change_global_data(void*)
{
global_semaphore.down();
++global_data;
std::cout &lt;&lt; &quot;global_data == &quot; &lt;&lt; global_data &lt;&lt; std::endl;
global_semaphore.up();
}
int main(int, char*[])
{
const int num_threads = 4;
boost::thread_group thrds;
for (int i=0; i &lt; num_threads; ++i)
thrds.create_thread(&amp;change_global_data, 0);
thrds.join_all();
return 0;
}
</pre>
<p>The output is:</p>
<pre>
global_data == 1
global_data == 2
global_data == 3
global_data == 4
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:shared_mutex Class `shared_mutex`]
#include <boost/thread/shared_mutex.hpp>
class shared_mutex
{
public:
shared_mutex();
~shared_mutex();
void lock_shared();
bool try_lock_shared();
bool timed_lock_shared(system_time const& timeout);
void unlock_shared();
void lock();
bool try_lock();
bool timed_lock(system_time const& timeout);
void unlock();
void lock_upgrade();
void unlock_upgrade();
void unlock_upgrade_and_lock();
void unlock_and_lock_upgrade();
void unlock_and_lock_shared();
void unlock_upgrade_and_lock_shared();
};
The class `boost::shared_mutex` provides an implementation of a multiple-reader / single-writer mutex. It implements the
__upgrade_lockable_concept__.
Multiple concurrent calls to __lock_ref__, __try_lock_ref__, __timed_lock_ref__, __lock_shared_ref__, __try_lock_shared_ref__ and
__timed_lock_shared_ref__ shall be permitted.
[endsect]

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{
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}

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/thread.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="thread">
<purpose>
<para>The <classname>thread</classname> class represents threads of
execution, and provides the functionality to create and manage
threads within the &Boost.Thread; library. See
<xref linkend="thread.glossary"/> for a precise description of
<link linkend="thread.glossary.thread">thread of execution</link>,
and for definitions of threading-related terms and of thread states such as
<link linkend="thread.glossary.thread-state">blocked</link>.</para>
</purpose>
<description>
<para>A <link linkend="thread.glossary.thread">thread of execution</link>
has an initial function. For the program's initial thread, the initial
function is <code>main()</code>. For other threads, the initial
function is <code>operator()</code> of the function object passed to
the <classname>thread</classname> object's constructor.</para>
<para>A thread of execution is said to be &quot;finished&quot;
or to have &quot;finished execution&quot; when its initial function returns or
is terminated. This includes completion of all thread cleanup
handlers, and completion of the normal C++ function return behaviors,
such as destruction of automatic storage (stack) objects and releasing
any associated implementation resources.</para>
<para>A thread object has an associated state which is either
&quot;joinable&quot; or &quot;non-joinable&quot;.</para>
<para>Except as described below, the policy used by an implementation
of &Boost.Thread; to schedule transitions between thread states is
unspecified.</para>
<para><note>Just as the lifetime of a file may be different from the
lifetime of an <code>iostream</code> object which represents the file, the lifetime
of a thread of execution may be different from the
<classname>thread</classname> object which represents the thread of
execution. In particular, after a call to <code>join()</code>,
the thread of execution will no longer exist even though the
<classname>thread</classname> object continues to exist until the
end of its normal lifetime. The converse is also possible; if
a <classname>thread</classname> object is destroyed without
<code>join()</code> first having been called, the thread of execution
continues until its initial function completes.</note></para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<constructor>
<effects>Constructs a <classname>thread</classname> object
representing the current thread of execution.</effects>
<postconditions><code>*this</code> is non-joinable.</postconditions>
<notes><emphasis role="bold">Danger:</emphasis>
<code>*this</code> is valid only within the current thread.</notes>
</constructor>
<constructor specifiers="explicit">
<parameter name="threadfunc">
<paramtype>const boost::function0&lt;void&gt;&amp;</paramtype>
</parameter>
<effects>
Starts a new thread of execution and constructs a
<classname>thread</classname> object representing it.
Copies <code>threadfunc</code> (which in turn copies
the function object wrapped by <code>threadfunc</code>)
to an internal location which persists for the lifetime
of the new thread of execution. Calls <code>operator()</code>
on the copy of the <code>threadfunc</code> function object
in the new thread of execution.
</effects>
<postconditions><code>*this</code> is joinable.</postconditions>
<throws><code>boost::thread_resource_error</code> if a new thread
of execution cannot be started.</throws>
</constructor>
<destructor>
<effects>Destroys <code>*this</code>. The actual thread of
execution may continue to execute after the
<classname>thread</classname> object has been destroyed.
</effects>
<notes>If <code>*this</code> is joinable the actual thread
of execution becomes &quot;detached&quot;. Any resources used
by the thread will be reclaimed when the thread of execution
completes. To ensure such a thread of execution runs to completion
before the <classname>thread</classname> object is destroyed, call
<code>join()</code>.</notes>
</destructor>
<method-group name="comparison">
<method name="operator==" cv="const">
<type>bool</type>
<parameter name="rhs">
<type>const thread&amp;</type>
</parameter>
<requires>The thread is non-terminated or <code>*this</code>
is joinable.</requires>
<returns><code>true</code> if <code>*this</code> and
<code>rhs</code> represent the same thread of
execution.</returns>
</method>
<method name="operator!=" cv="const">
<type>bool</type>
<parameter name="rhs">
<type>const thread&amp;</type>
</parameter>
<requires>The thread is non-terminated or <code>*this</code>
is joinable.</requires>
<returns><code>!(*this==rhs)</code>.</returns>
</method>
</method-group>
<method-group name="modifier">
<method name="join">
<type>void</type>
<requires><code>*this</code> is joinable.</requires>
<effects>The current thread of execution blocks until the
initial function of the thread of execution represented by
<code>*this</code> finishes and all resources are
reclaimed.</effects>
<postcondition><code>*this</code> is non-joinable.</postcondition>
<notes>If <code>*this == thread()</code> the result is
implementation-defined. If the implementation doesn't
detect this the result will be
<link linkend="thread.glossary.deadlock">deadlock</link>.
</notes>
</method>
</method-group>
<method-group name="static">
<method name="sleep" specifiers="static">
<type>void</type>
<parameter name="xt">
<paramtype>const <classname>xtime</classname>&amp;</paramtype>
</parameter>
<effects>The current thread of execution blocks until
<code>xt</code> is reached.</effects>
</method>
<method name="yield" specifiers="static">
<type>void</type>
<effects>The current thread of execution is placed in the
<link linkend="thread.glossary.thread-state">ready</link>
state.</effects>
<notes>
<simpara>Allow the current thread to give up the rest of its
time slice (or other scheduling quota) to another thread.
Particularly useful in non-preemptive implementations.</simpara>
</notes>
</method>
</method-group>
</class>
<class name="thread_group">
<purpose>
The <classname>thread_group</classname> class provides a container
for easy grouping of threads to simplify several common thread
creation and management idioms.
</purpose>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<constructor>
<effects>Constructs an empty <classname>thread_group</classname>
container.</effects>
</constructor>
<destructor>
<effects>Destroys each contained thread object. Destroys <code>*this</code>.</effects>
<notes>Behavior is undefined if another thread references
<code>*this </code> during the execution of the destructor.
</notes>
</destructor>
<method-group name="modifier">
<method name="create_thread">
<type><classname>thread</classname>*</type>
<parameter name="threadfunc">
<paramtype>const boost::function0&lt;void&gt;&amp;</paramtype>
</parameter>
<effects>Creates a new <classname>thread</classname> object
that executes <code>threadfunc</code> and adds it to the
<code>thread_group</code> container object's list of managed
<classname>thread</classname> objects.</effects>
<returns>Pointer to the newly created
<classname>thread</classname> object.</returns>
</method>
<method name="add_thread">
<type>void</type>
<parameter name="thrd">
<paramtype><classname>thread</classname>*</paramtype>
</parameter>
<effects>Adds <code>thrd</code> to the
<classname>thread_group</classname> object's list of managed
<classname>thread</classname> objects. The <code>thrd</code>
object must have been allocated via <code>operator new</code> and will
be deleted when the group is destroyed.</effects>
</method>
<method name="remove_thread">
<type>void</type>
<parameter name="thrd">
<paramtype><classname>thread</classname>*</paramtype>
</parameter>
<effects>Removes <code>thread</code> from <code>*this</code>'s
list of managed <classname>thread</classname> objects.</effects>
<throws><emphasis role="bold">???</emphasis> if
<code>thrd</code> is not in <code>*this</code>'s list
of managed <classname>thread</classname> objects.</throws>
</method>
<method name="join_all">
<type>void</type>
<effects>Calls <code>join()</code> on each of the managed
<classname>thread</classname> objects.</effects>
</method>
</method-group>
</class>
</namespace>
</header>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, Boost.Threads, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, thread</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Class thread</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Members">Members</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>thread</code> class represents threads of execution, and provides
the functionality to create and manage threads within the <b>Boost.Threads</b>
library. See <A href="definitions.html">Definitions</A> for a precise description of
"thread of execution", and for definitions of threading related terms and of thread
states such as "blocked".</p>
<p>A thread of execution has an initial function. For the program's
initial thread, the initial function is <code>main()</code>. For other
threads, the initial function is <code>operator()</code> of the function object
passed to the class <code>thread</code> constructor.</p>
<p>A thread of execution is said to be "finished" or "finished execution" when its
initial function returns or is terminated. This includes completion of all thread
cleanup handlers, and completion of the normal C++ function return behaviors, such
as destruction of automatic storage (stack) objects and releasing any associated
implementation resources.</p>
<p>A thread object has an associated state which is either "joinable" or
"non-joinable".</p>
<p>Except as described below, the policy used by an implementation of
<b>Boost.Threads</b> to schedule transitions between thread states is unspecified.</p>
<p><b>Note: </b>Just as the lifetime of a file may be different from the
lifetime of an iostream object which represents the file, the lifetime of a
thread of execution may be different from the <code>thread</code> object which
represents the thread of execution. In particular, after a call to <code>join()</code>,
the thread of execution will no longer exist even though the <code>thread</code>
object continues to exist until the end of its normal lifetime. The
converse is also possible; if a <code>thread</code> object is destroyed without
<code>join()</code> having first been called, the thread of execution continues until
its initial function completes.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <A href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</A>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
class thread : <a href="../../utility/utility.htm#noncopyable">boost::noncopyable</a> // Exposition only.
// Class thread meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
thread();
explicit thread(const boost::function0&lt;void&gt;&amp; threadfunc);
~thread();
bool operator==(const thread&amp; rhs) const;
bool operator!=(const thread&amp; rhs) const;
void join();
static void sleep(const xtime&amp; xt);
static void yield();
};
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructors</h3>
<pre>
thread();
</pre>
<p><b>Effects:</b> Constructs a <code>thread</code> object representing the current thread
of execution.</p>
<p><b>Postcondition:</b> <code>*this</code> is non-joinable.</p>
<p><b>Danger:</b> <code>*this</code> is valid only within the current thread.</p>
<pre>
thread(const <A href="../../function/index.html">boost::function0</A>&lt;void&gt;&amp; threadfunc);
</pre>
<p><b>Effects:</b> Starts a new thread of execution and constructs a <code>thread</code> object
representing it. Copies <code>threadfunc</code>
(which in turn copies the function object wrapped by <code>threadfunc</code>) to an
internal location which persists for the lifetime of the new thread of execution. Calls
<code>operator()</code> on the copy of the <code>threadfunc</code> function object in
the new thread of execution.</p>
<p><b>Postcondition:</b> <code>*this</code> is joinable.</p>
<p><b>Throws:</b> <code>boost::thread_resource_error</code> if a new thread of execution
cannot be started.</p>
<hr>
<h3>Destructor</h3>
<pre>
~thread();
</pre>
<p><b>Effects:</b> Destroys <code>*this</code>. The actual thread of execution may
continue to execute after the <code>thread</code> object has been destroyed.</p>
<p><b>Notes:</b> If <code>*this</code> is joinable the actual thread of execution
becomes "detached". Any resources used by the thread will be reclaimed when the
thread of execution completes. To ensure such a thread of execution runs to completion
before the <code>thread</code> object is destroyed, call <code>join()</code>.</p>
<hr>
<h3>Comparison Operators</h3>
<pre>
bool operator==(const thread&amp; rhs);
</pre>
<p><b>Requires:</b> The thread is non-terminated or <code>*this</code> is joinable.</p>
<p><b>Returns:</b> <code>true</code> if <code>*this</code> and <code>rhs</code>
represent the same thread of execution.</p>
<pre>
bool operator!=(const thread&amp; rhs);
</pre>
<p><b>Returns:</b> <code>!(*this==rhs)</code>.</p>
<hr>
<h3>join</h3>
<pre>
void join();
</pre>
<p><b>Requires:</b> <code>*this</code> is joinable.</p>
<p><b>Effects:</b> The current thread of execution blocks until the initial function of
the thread of execution represented by <code>*this</code> finishes and all resources
are reclaimed.</p>
<p><b>Postcondition:</b> <code>*this</code> is non-joinable.</p>
<p><b>Note:</b></p> If <code>*this == thread()</code> the result is implementation defined.
If the implementation doesn't detect this the result will be
<a href="definitions.html#Deadlock">deadlock</a>.</p>
<hr>
<h3>sleep</h3>
<pre>
static void sleep(const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Effects:</b> The current thread of execution blocks until <code>xt</code> is
reached.</p>
<hr>
<h3>yield</h3>
<pre>
static void yield();
</pre>
<p><b>Effects:</b> The current thread of execution is placed in the "ready" state.</p>
<p><b>Notes:</b> Allow the current thread to give up the rest of its time slice
(or other scheduling quota) to another thread. Particularly useful in non-preemptive
implementations.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include &lt;boost/thread/thread.hpp&gt;
#include &lt;iostream&gt;
struct thread_alarm
{
thread_alarm(int secs) : m_secs(secs) { }
void operator()()
{
boost::xtime xt;
boost::xtime_get(&amp;xt, boost::TIME_UTC);
xt.sec += m_secs;
boost::thread::sleep(xt);
std::cout &lt;&lt; &quot;alarm sounded...&quot; &lt;&lt; std::endl;
}
int m_secs;
};
int main(int argc, char* argv[])
{
int secs = 5;
std::cout &lt;&lt; &quot;setting alarm for 5 seconds...&quot; &lt;&lt; std::endl;
boost::thread thrd(thread_alarm(secs));
thrd.join();
}
</pre>
<p>The output is:</p>
<pre>
setting alarm for 5 seconds...
alarm sounded...
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</A>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -1,167 +0,0 @@
[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[article Thread
[quickbook 1.4]
[authors [Williams, Anthony]]
[copyright 2007-8 Anthony Williams]
[purpose C++ Library for launching threads and synchronizing data between them]
[category text]
[license
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
[@http://www.boost.org/LICENSE_1_0.txt])
]
]
[template lockable_concept_link[link_text] [link thread.synchronization.mutex_concepts.lockable [link_text]]]
[def __lockable_concept__ [lockable_concept_link `Lockable` concept]]
[def __lockable_concept_type__ [lockable_concept_link `Lockable`]]
[template timed_lockable_concept_link[link_text] [link thread.synchronization.mutex_concepts.timed_lockable [link_text]]]
[def __timed_lockable_concept__ [timed_lockable_concept_link `TimedLockable` concept]]
[def __timed_lockable_concept_type__ [timed_lockable_concept_link `TimedLockable`]]
[template shared_lockable_concept_link[link_text] [link thread.synchronization.mutex_concepts.shared_lockable [link_text]]]
[def __shared_lockable_concept__ [shared_lockable_concept_link `SharedLockable` concept]]
[def __shared_lockable_concept_type__ [shared_lockable_concept_link `SharedLockable`]]
[template upgrade_lockable_concept_link[link_text] [link thread.synchronization.mutex_concepts.upgrade_lockable [link_text]]]
[def __upgrade_lockable_concept__ [upgrade_lockable_concept_link `UpgradeLockable` concept]]
[def __upgrade_lockable_concept_type__ [upgrade_lockable_concept_link `UpgradeLockable`]]
[template lock_ref_link[link_text] [link thread.synchronization.mutex_concepts.lockable.lock [link_text]]]
[def __lock_ref__ [lock_ref_link `lock()`]]
[template lock_multiple_ref_link[link_text] [link thread.synchronization.lock_functions.lock_multiple [link_text]]]
[def __lock_multiple_ref__ [lock_multiple_ref_link `lock()`]]
[template try_lock_multiple_ref_link[link_text] [link thread.synchronization.lock_functions.try_lock_multiple [link_text]]]
[def __try_lock_multiple_ref__ [try_lock_multiple_ref_link `try_lock()`]]
[template unlock_ref_link[link_text] [link thread.synchronization.mutex_concepts.lockable.unlock [link_text]]]
[def __unlock_ref__ [unlock_ref_link `unlock()`]]
[template try_lock_ref_link[link_text] [link thread.synchronization.mutex_concepts.lockable.try_lock [link_text]]]
[def __try_lock_ref__ [try_lock_ref_link `try_lock()`]]
[template timed_lock_ref_link[link_text] [link thread.synchronization.mutex_concepts.timed_lockable.timed_lock [link_text]]]
[def __timed_lock_ref__ [timed_lock_ref_link `timed_lock()`]]
[template timed_lock_duration_ref_link[link_text] [link thread.synchronization.mutex_concepts.timed_lockable.timed_lock_duration [link_text]]]
[def __timed_lock_duration_ref__ [timed_lock_duration_ref_link `timed_lock()`]]
[template lock_shared_ref_link[link_text] [link thread.synchronization.mutex_concepts.shared_lockable.lock_shared [link_text]]]
[def __lock_shared_ref__ [lock_shared_ref_link `lock_shared()`]]
[template unlock_shared_ref_link[link_text] [link thread.synchronization.mutex_concepts.shared_lockable.unlock_shared [link_text]]]
[def __unlock_shared_ref__ [unlock_shared_ref_link `unlock_shared()`]]
[template try_lock_shared_ref_link[link_text] [link thread.synchronization.mutex_concepts.shared_lockable.try_lock_shared [link_text]]]
[def __try_lock_shared_ref__ [try_lock_shared_ref_link `try_lock_shared()`]]
[template timed_lock_shared_ref_link[link_text] [link thread.synchronization.mutex_concepts.shared_lockable.timed_lock_shared [link_text]]]
[def __timed_lock_shared_ref__ [timed_lock_shared_ref_link `timed_lock_shared()`]]
[template timed_lock_shared_duration_ref_link[link_text] [link thread.synchronization.mutex_concepts.shared_lockable.timed_lock_shared_duration [link_text]]]
[def __timed_lock_shared_duration_ref__ [timed_lock_shared_duration_ref_link `timed_lock_shared()`]]
[template lock_upgrade_ref_link[link_text] [link thread.synchronization.mutex_concepts.upgrade_lockable.lock_upgrade [link_text]]]
[def __lock_upgrade_ref__ [lock_upgrade_ref_link `lock_upgrade()`]]
[template unlock_upgrade_ref_link[link_text] [link thread.synchronization.mutex_concepts.upgrade_lockable.unlock_upgrade [link_text]]]
[def __unlock_upgrade_ref__ [unlock_upgrade_ref_link `unlock_upgrade()`]]
[template unlock_upgrade_and_lock_ref_link[link_text] [link thread.synchronization.mutex_concepts.upgrade_lockable.unlock_upgrade_and_lock [link_text]]]
[def __unlock_upgrade_and_lock_ref__ [unlock_upgrade_and_lock_ref_link `unlock_upgrade_and_lock()`]]
[template unlock_and_lock_upgrade_ref_link[link_text] [link thread.synchronization.mutex_concepts.upgrade_lockable.unlock_and_lock_upgrade [link_text]]]
[def __unlock_and_lock_upgrade_ref__ [unlock_and_lock_upgrade_ref_link `unlock_and_lock_upgrade()`]]
[template unlock_upgrade_and_lock_shared_ref_link[link_text] [link thread.synchronization.mutex_concepts.upgrade_lockable.unlock_upgrade_and_lock_shared [link_text]]]
[def __unlock_upgrade_and_lock_shared_ref__ [unlock_upgrade_and_lock_shared_ref_link `unlock_upgrade_and_lock_shared()`]]
[template owns_lock_ref_link[link_text] [link thread.synchronization.locks.unique_lock.owns_lock [link_text]]]
[def __owns_lock_ref__ [owns_lock_ref_link `owns_lock()`]]
[template owns_lock_shared_ref_link[link_text] [link thread.synchronization.locks.shared_lock.owns_lock [link_text]]]
[def __owns_lock_shared_ref__ [owns_lock_shared_ref_link `owns_lock()`]]
[template mutex_func_ref_link[link_text] [link thread.synchronization.locks.unique_lock.mutex [link_text]]]
[def __mutex_func_ref__ [mutex_func_ref_link `mutex()`]]
[def __boost_thread__ [*Boost.Thread]]
[def __not_a_thread__ ['Not-a-Thread]]
[def __interruption_points__ [link interruption_points ['interruption points]]]
[def __mutex__ [link thread.synchronization.mutex_types.mutex `boost::mutex`]]
[def __try_mutex__ [link thread.synchronization.mutex_types.try_mutex `boost::try_mutex`]]
[def __timed_mutex__ [link thread.synchronization.mutex_types.timed_mutex `boost::timed_mutex`]]
[def __recursive_mutex__ [link thread.synchronization.mutex_types.recursive_mutex `boost::recursive_mutex`]]
[def __recursive_try_mutex__ [link thread.synchronization.mutex_types.recursive_try_mutex `boost::recursive_try_mutex`]]
[def __recursive_timed_mutex__ [link thread.synchronization.mutex_types.recursive_timed_mutex `boost::recursive_timed_mutex`]]
[def __shared_mutex__ [link thread.synchronization.mutex_types.shared_mutex `boost::shared_mutex`]]
[template unique_lock_link[link_text] [link thread.synchronization.locks.unique_lock [link_text]]]
[def __lock_guard__ [link thread.synchronization.locks.lock_guard `boost::lock_guard`]]
[def __unique_lock__ [unique_lock_link `boost::unique_lock`]]
[def __shared_lock__ [link thread.synchronization.locks.shared_lock `boost::shared_lock`]]
[def __upgrade_lock__ [link thread.synchronization.locks.upgrade_lock `boost::upgrade_lock`]]
[def __upgrade_to_unique_lock__ [link thread.synchronization.locks.upgrade_to_unique_lock `boost::upgrade_to_unique_lock`]]
[def __thread__ [link thread.thread_management.thread `boost::thread`]]
[def __thread_id__ [link thread.thread_management.thread.id `boost::thread::id`]]
[template join_link[link_text] [link thread.thread_management.thread.join [link_text]]]
[def __join__ [join_link `join()`]]
[template timed_join_link[link_text] [link thread.thread_management.thread.timed_join [link_text]]]
[def __timed_join__ [timed_join_link `timed_join()`]]
[def __detach__ [link thread.thread_management.thread.detach `detach()`]]
[def __interrupt__ [link thread.thread_management.thread.interrupt `interrupt()`]]
[def __sleep__ [link thread.thread_management.this_thread.sleep `boost::this_thread::sleep()`]]
[def __interruption_enabled__ [link thread.thread_management.this_thread.interruption_enabled `boost::this_thread::interruption_enabled()`]]
[def __interruption_requested__ [link thread.thread_management.this_thread.interruption_requested `boost::this_thread::interruption_requested()`]]
[def __interruption_point__ [link thread.thread_management.this_thread.interruption_point `boost::this_thread::interruption_point()`]]
[def __disable_interruption__ [link thread.thread_management.this_thread.disable_interruption `boost::this_thread::disable_interruption`]]
[def __restore_interruption__ [link thread.thread_management.this_thread.restore_interruption `boost::this_thread::restore_interruption`]]
[def __thread_resource_error__ `boost::thread_resource_error`]
[def __thread_interrupted__ `boost::thread_interrupted`]
[def __barrier__ [link thread.synchronization.barriers.barrier `boost::barrier`]]
[template cond_wait_link[link_text] [link thread.synchronization.condvar_ref.condition_variable.wait [link_text]]]
[def __cond_wait__ [cond_wait_link `wait()`]]
[template cond_timed_wait_link[link_text] [link thread.synchronization.condvar_ref.condition_variable.timed_wait [link_text]]]
[def __cond_timed_wait__ [cond_timed_wait_link `timed_wait()`]]
[template cond_any_wait_link[link_text] [link thread.synchronization.condvar_ref.condition_variable_any.wait [link_text]]]
[def __cond_any_wait__ [cond_any_wait_link `wait()`]]
[template cond_any_timed_wait_link[link_text] [link thread.synchronization.condvar_ref.condition_variable_any.timed_wait [link_text]]]
[def __cond_any_timed_wait__ [cond_any_timed_wait_link `timed_wait()`]]
[def __blocked__ ['blocked]]
[include overview.qbk]
[include changes.qbk]
[include thread_ref.qbk]
[section:synchronization Synchronization]
[include mutex_concepts.qbk]
[include mutexes.qbk]
[include condition_variables.qbk]
[include once.qbk]
[include barrier.qbk]
[endsect]
[include tss.qbk]
[include time.qbk]
[include acknowledgements.qbk]

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@@ -1,48 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<library name="Thread" dirname="thread" id="thread"
last-revision="$Date$"
xmlns:xi="http://www.w3.org/2001/XInclude">
<libraryinfo>
<author>
<firstname>William</firstname>
<othername>E.</othername>
<surname>Kempf</surname>
</author>
<copyright>
<year>2001</year>
<year>2002</year>
<year>2003</year>
<holder>William E. Kempf</holder>
</copyright>
<legalnotice>
<para>Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)</para>
</legalnotice>
<librarypurpose>Portable C++ multi-threading</librarypurpose>
<librarycategory name="category:concurrent" />
<title>Boost.Thread</title>
</libraryinfo>
<title>Boost.Thread</title>
<xi:include href="overview.xml"/>
<xi:include href="design.xml"/>
<xi:include href="concepts.xml"/>
<xi:include href="rationale.xml"/>
<xi:include href="reference.xml"/>
<xi:include href="faq.xml"/>
<xi:include href="configuration.xml"/>
<xi:include href="build.xml"/>
<xi:include href="implementation_notes.xml"/>
<xi:include href="release_notes.xml"/>
<xi:include href="glossary.xml"/>
<xi:include href="acknowledgements.xml"/>
<xi:include href="bibliography.xml"/>
</library>

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doc/thread_group.html Normal file
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@@ -0,0 +1,187 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, thread_group</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">thread_group</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt>thread_group</tt> class provides a container for easy grouping of threads to simplify several
common thread creation and management idioms.</p>
<p>All <tt>thread_group</tt> member functions are <a href="definitions.html#thread-safe">thread-safe</a>,
except destruction.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
{
class thread_group : <a href="../../utility/utility.htm#noncopyable">boost::noncopyable</a>
{
public:
thread_group();
~thread_group();
thread* create_thread(const boost::function0&lt;void&gt;&amp; threadfunc);
void add_thread(thread* thrd);
void remove_thread(thread* thrd);
void join_all();
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
thread_group();
</pre>
<p><b>Effects:</b> Constructs an empty <tt>thread_group</tt> container.</p>
<hr>
<h3>Destructor</h3>
<pre>
~thread_group();
</pre>
<p><b>Effects:</b> Destroys each contained thread object.&nbsp; Destroys <code>*this</code>.</p>
<p><b>Notes:</b> Behavior is undefined if another thread references *this during
the execution of the destructor.</p>
<hr>
<h3>create_thread</h3>
<pre>
thread* create_thread(const boost::function0&lt;void&gt;&amp; threadfunc);
</pre>
<p><b>Effects:</b> Creates a new <tt>thread</tt> object that executes <tt>threadfunc</tt> and adds it to the
<tt>thread_group</tt> container object's list of managed <tt>thread</tt> objects.</p>
<p><b>Returns:</b> Pointer to the newly created thread.</p>
<hr>
<h3>add_thread</h3>
<pre>
void add_thread(thread* thrd);
</pre>
<p><b>Effects:</b> Adds <tt>thrd</tt> to the <tt>thread_group</tt> object's list of managed <tt>thread</tt>
objects. The <tt>thrd</tt> object must have been allocated via operator new and will
be deleted when the group is destroyed.</p>
<hr>
<h3>remove_thread</h3>
<pre>
void remove_thread(thread* thrd);
</pre>
<p><b>Effects:</b> Removes <code>*this</code>'s list of managed <tt>thread</tt>
objects.</p>
<p><b>Throws: </b>? if <tt>thrd</tt> is not it <code>*this</code>'s list of managed <tt>thread</tt>
objects.</p>
<hr>
<h3>join_all</h3>
<pre>
void join_all();
</pre>
<p><b>Effects:</b> Calls <code> join()</code> on each of the managed <tt>thread</tt> objects.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include &lt;boost/thread/thread.hpp&gt;
#include &lt;iostream&gt;
int count = 0;
boost::mutex mutex;
void increment_count()
{
boost::mutex::lock lock(mutex);
std::cout &lt;&lt; &quot;count = &quot; &lt;&lt; ++count &lt;&lt; std::endl;
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i = 0; i &lt; 10; ++i)
threads.create_thread(&amp;increment_count);
threads.join_all();
}
</pre>
<p>The output is:</p>
<pre>
count = 1
count = 2
count = 3
count = 4
count = 5
count = 6
count = 7
count = 8
count = 9
count = 10
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->06 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34352" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, thread_resource_error</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">thread_resource_error</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>thread_resource_error</code> class defines an exception type that is thrown
by constructors in the <b>Boost.Threads</b> library when thread related resources
can not be
acquired. This does not include memory allocation failures which instead throw
std::bad_alloc.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/exceptions.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
{
class thread_resource_error : public std::runtime_error
{
public:
thread_resource_error();
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
thread_resource_error();
</pre>
<p>Constructs a <code>thread_resource_error</code> object.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->04 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39335" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, Boost.Threads, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, thread_specific_ptr</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">thread_specific_ptr</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Members">Members</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>thread_specific_ptr</code> class defines an interface for using thread
specific storage. Thread specific storage is data associated with individual threads
and is often used to make operations
<a href="definitions.html#Thread-safe">thread-safe</a> that rely on global data.</p>
<p>Template <code>thread_specific_ptr</code> stores a pointer to an object obtained via
<code>new</code> on a thread-by-thread basis and calls delete on the contained pointer
when the thread terminates. Each thread initially stores the null pointer in each
<code>thread_specific_ptr</code> instance.</p>
<p>The template <code>thread_specific_ptr</code> is useful in the following cases:</p>
<ul>
<li>An interface was original written assuming a single thread of control and is
being ported to a multi-threaded environment.</li>
<li>Each thread of control invokes sequences of methods that share data that must be
logically accessed through a globally visible access point, but are physically
unique for each thread, instead of being explicitly passed.</li>
</ul>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/tss.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
template &lt;typename T&gt;
class thread_specific_ptr : private boost::noncopyable // Exposition only.
// Class thread_specific_ptr meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
thread_specific_ptr();
~thread_specific_ptr();
T* get() const;
T* operator-&gt;() const;
T&amp; operator*() const;
T* release();
void reset(T* p=0);
};
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
thread_specific_ptr();
</pre>
<p><b>Postconditions:</b> A thread specific storage has been reserved for use by *this
in all threads, with each thread initially storing a null pointer.</p>
<p><b>Requires:</b> The expression <code>delete get()</code> is well formed.</p>
<p><b>Throws:</b> <code>boost::thread_resource_error</code> if the necessary resources
can not be obtained.</p>
<p><b>Notes:</b> There is an implementation specific limit to the number of thread
specific storage objects that can be created, and this limit may be small.</p>
<hr>
<h3>Destructor</h3>
<pre>
~thread_specific_ptr();
</pre>
<p><b>Notes:</b> Does not destroy any data that may be stored in any thread's thread
specific storage. For this reason you should not destroy a
<code>thread_specific_ptr</code> object until you are certain there are no threads
running that have made use of its thread specific storage.</p>
<hr>
<h3>get</h3>
<pre>
T* get() const;
</pre>
<p><b>Returns:</b> The object stored in thread specific storage for the current thread
for *this.</p>
<p><b>Notes:</b> Each thread initially returns 0.</p>
<hr>
<h3>Smart Pointer Operations</h3>
<pre>
T* operator-&gt;() const;
</pre>
<p><b>Returns:</b> <code>get()</code></p>
<pre>
T&amp; operator*() const;
</pre>
<p><b>Returns:</b> <code>get()</code></p>
<p><b>Requires:</b> <code>get() != 0</code></p>
<hr>
<h3>Release</h3>
<pre>
T* release();
</pre>
<p><b>Returns:</b> <code>get()</code></p>
<p><b>Postcondition:</b> *this holds the null pointer for the current thread.</p>
<hr>
<h3>Reset</h3>
<pre>
void reset(T* p=0);
</pre>
<p><b>Effects:</b> If <code>get()!= p</code> then <code>delete get()</code>.</p>
<p><b>Postconditions:</b> <code>*this</code> holds the pointer <code>p</code> for
the current thread.</p>
<p><b>Notes:</b> The pointer will be deleted when the thread terminates.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/tss.hpp&gt;</a>
#include &lt;cassert&gt;
boost::thread_specific_ptr&lt;int&gt; value;
void increment()
{
int* p = value.get();
++*p;
}
void thread_proc()
{
value.reset(new int(0)); // initialize the thread's storage
for (int i=0; i&lt;10; ++i)
{
increment();
int* p = value.get();
assert(*p == i+1);
}
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i&lt;5; ++i)
threads.create_thread(&amp;thread_proc);
threads.join_all();
}
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:time Date and Time Requirements]
As of Boost 1.35.0, the __boost_thread__ library uses the [link date_time Boost.Date_Time] library for all operations that require a
time out. These include (but are not limited to):
* __sleep__
* __timed_join__
* __cond_timed_wait__
* __timed_lock_ref__
For the overloads that accept an absolute time parameter, an object of type [link thread.time.system_time `boost::system_time`] is
required. Typically, this will be obtained by adding a duration to the current time, obtained with a call to [link
thread.time.get_system_time `boost::get_system_time()`]. e.g.
boost::system_time const timeout=boost::get_system_time() + boost::posix_time::milliseconds(500);
extern bool done;
extern boost::mutex m;
extern boost::condition_variable cond;
boost::unique_lock<boost::mutex> lk(m);
while(!done)
{
if(!cond.timed_wait(lk,timeout))
{
throw "timed out";
}
}
For the overloads that accept a ['TimeDuration] parameter, an object of any type that meets the [link
date_time.posix_time.time_duration Boost.Date_Time Time Duration requirements] can be used, e.g.
boost::this_thread::sleep(boost::posix_time::milliseconds(25));
boost::mutex m;
if(m.timed_lock(boost::posix_time::nanoseconds(100)))
{
// ...
}
[section:system_time Typedef `system_time`]
#include <boost/thread/thread_time.hpp>
typedef boost::posix_time::ptime system_time;
See the documentation for [link date_time.posix_time.ptime_class `boost::posix_time::ptime`] in the Boost.Date_Time library.
[endsect]
[section:get_system_time Non-member function `get_system_time()`]
#include <boost/thread/thread_time.hpp>
system_time get_system_time();
[variablelist
[[Returns:] [The current time.]]
[[Throws:] [Nothing.]]
]
[endsect]
[endsect]

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/tss.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="thread_specific_ptr">
<purpose>
The <classname>thread_specific_ptr</classname> class defines
an interface for using thread specific storage.
</purpose>
<description>
<para>Thread specific storage is data associated with
individual threads and is often used to make operations
that rely on global data
<link linkend="thread.glossary.thread-safe">thread-safe</link>.
</para>
<para>Template <classname>thread_specific_ptr</classname>
stores a pointer to an object obtained on a thread-by-thread
basis and calls a specified cleanup handler on the contained
pointer when the thread terminates. The cleanup handlers are
called in the reverse order of construction of the
<classname>thread_specific_ptr</classname>s, and for the
initial thread are called by the destructor, providing the
same ordering guarantees as for normal declarations. Each
thread initially stores the null pointer in each
<classname>thread_specific_ptr</classname> instance.</para>
<para>The template <classname>thread_specific_ptr</classname>
is useful in the following cases:
<itemizedlist>
<listitem>An interface was originally written assuming
a single thread of control and it is being ported to a
multithreaded environment.</listitem>
<listitem>Each thread of control invokes sequences of
methods that share data that are physically unique
for each thread, but must be logically accessed
through a globally visible access point instead of
being explicitly passed.</listitem>
</itemizedlist>
</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<constructor>
<requires>The expression <code>delete get()</code> is well
formed.</requires>
<effects>A thread-specific data key is allocated and visible to
all threads in the process. Upon creation, the value
<code>NULL</code> will be associated with the new key in all
active threads. A cleanup method is registered with the key
that will call <code>delete</code> on the value associated
with the key for a thread when it exits. When a thread exits,
if a key has a registered cleanup method and the thread has a
non-<code>NULL</code> value associated with that key, the value
of the key is set to <code>NULL</code> and then the cleanup
method is called with the previously associated value as its
sole argument. The order in which registered cleanup methods
are called when a thread exits is undefined. If after all the
cleanup methods have been called for all non-<code>NULL</code>
values, there are still some non-<code>NULL</code> values
with associated cleanup handlers the result is undefined
behavior.</effects>
<throws><classname>boost::thread_resource_error</classname> if
the necessary resources can not be obtained.</throws>
<notes>There may be an implementation specific limit to the
number of thread specific storage objects that can be created,
and this limit may be small.</notes>
<rationale>The most common need for cleanup will be to call
<code>delete</code> on the associated value. If other forms
of cleanup are required the overloaded constructor should be
called instead.</rationale>
</constructor>
<constructor>
<parameter name="cleanup">
<paramtype>void (*cleanup)(void*)</paramtype>
</parameter>
<effects>A thread-specific data key is allocated and visible to
all threads in the process. Upon creation, the value
<code>NULL</code> will be associated with the new key in all
active threads. The <code>cleanup</code> method is registered
with the key and will be called for a thread with the value
associated with the key for that thread when it exits. When a
thread exits, if a key has a registered cleanup method and the
thread has a non-<code>NULL</code> value associated with that
key, the value of the key is set to <code>NULL</code> and then
the cleanup method is called with the previously associated
value as its sole argument. The order in which registered
cleanup methods are called when a thread exits is undefined.
If after all the cleanup methods have been called for all
non-<code>NULL</code> values, there are still some
non-<code>NULL</code> values with associated cleanup handlers
the result is undefined behavior.</effects>
<throws><classname>boost::thread_resource_error</classname> if
the necessary resources can not be obtained.</throws>
<notes>There may be an implementation specific limit to the
number of thread specific storage objects that can be created,
and this limit may be small.</notes>
<rationale>There is the occasional need to register
specialized cleanup methods, or to register no cleanup method
at all (done by passing <code>NULL</code> to this constructor.
</rationale>
</constructor>
<destructor>
<effects>Deletes the thread-specific data key allocated by the
constructor. The thread-specific data values associated with
the key need not be <code>NULL</code>. It is the responsibility
of the application to perform any cleanup actions for data
associated with the key.</effects>
<notes>Does not destroy any data that may be stored in any
thread's thread specific storage. For this reason you should
not destroy a <classname>thread_specific_ptr</classname> object
until you are certain there are no threads running that have
made use of its thread specific storage.</notes>
<rationale>Associated data is not cleaned up because registered
cleanup methods need to be run in the thread that allocated the
associated data to be guarranteed to work correctly. There's no
safe way to inject the call into another thread's execution
path, making it impossible to call the cleanup methods safely.
</rationale>
</destructor>
<method-group name="modifier functions">
<method name="release">
<type>T*</type>
<postconditions><code>*this</code> holds the null pointer
for the current thread.</postconditions>
<returns><code>this-&gt;get()</code> prior to the call.</returns>
<rationale>This method provides a mechanism for the user to
relinquish control of the data associated with the
thread-specific key.</rationale>
</method>
<method name="reset">
<type>void</type>
<parameter name="p">
<paramtype>T*</paramtype>
<default>0</default>
</parameter>
<effects>If <code>this-&gt;get() != p &amp;&amp;
this-&gt;get() != NULL</code> then call the
associated cleanup function.</effects>
<postconditions><code>*this</code> holds the pointer
<code>p</code> for the current thread.</postconditions>
</method>
</method-group>
<method-group name="observer functions">
<method name="get" cv="const">
<type>T*</type>
<returns>The object stored in thread specific storage for
the current thread for <code>*this</code>.</returns>
<notes>Each thread initially returns 0.</notes>
</method>
<method name="operator-&gt;" cv="const">
<type>T*</type>
<returns><code>this-&gt;get()</code>.</returns>
</method>
<method name="operator*()" cv="const">
<type>T&amp;</type>
<requires><code>this-&gt;get() != 0</code></requires>
<returns><code>this-&gt;get()</code>.</returns>
</method>
</method-group>
</class>
</namespace>
</header>

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[/
(C) Copyright 2007-8 Anthony Williams.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section Thread Local Storage]
[heading Synopsis]
Thread local storage allows multi-threaded applications to have a separate instance of a given data item for each thread. Where a
single-threaded application would use static or global data, this could lead to contention, deadlock or data corruption in a
multi-threaded application. One example is the C `errno` variable, used for storing the error code related to functions from the
Standard C library. It is common practice (and required by POSIX) for compilers that support multi-threaded applications to provide
a separate instance of `errno` for each thread, in order to avoid different threads competing to read or update the value.
Though compilers often provide this facility in the form of extensions to the declaration syntax (such as `__declspec(thread)` or
`__thread` annotations on `static` or namespace-scope variable declarations), such support is non-portable, and is often limited in
some way, such as only supporting POD types.
[heading Portable thread-local storage with `boost::thread_specific_ptr`]
`boost::thread_specific_ptr` provides a portable mechanism for thread-local storage that works on all compilers supported by
__boost_thread__. Each instance of `boost::thread_specific_ptr` represents a pointer to an object (such as `errno`) where each
thread must have a distinct value. The value for the current thread can be obtained using the `get()` member function, or by using
the `*` and `->` pointer deference operators. Initially the pointer has a value of `NULL` in each thread, but the value for the
current thread can be set using the `reset()` member function.
If the value of the pointer for the current thread is changed using `reset()`, then the previous value is destroyed by calling the
cleanup routine. Alternatively, the stored value can be reset to `NULL` and the prior value returned by calling the `release()`
member function, allowing the application to take back responsibility for destroying the object.
[heading Cleanup at thread exit]
When a thread exits, the objects associated with each `boost::thread_specific_ptr` instance are destroyed. By default, the object
pointed to by a pointer `p` is destroyed by invoking `delete p`, but this can be overridden for a specific instance of
`boost::thread_specific_ptr` by providing a cleanup routine to the constructor. In this case, the object is destroyed by invoking
`func(p)` where `func` is the cleanup routine supplied to the constructor. The cleanup functions are called in an unspecified
order. If a cleanup routine sets the value of associated with an instance of `boost::thread_specific_ptr` that has already been
cleaned up, that value is added to the cleanup list. Cleanup finishes when there are no outstanding instances of
`boost::thread_specific_ptr` with values.
[section:thread_specific_ptr Class `thread_specific_ptr`]
#include <boost/thread/tss.hpp>
template <typename T>
class thread_specific_ptr
{
public:
thread_specific_ptr();
explicit thread_specific_ptr(void (*cleanup_function)(T*));
~thread_specific_ptr();
T* get() const;
T* operator->() const;
T& operator*() const;
T* release();
void reset(T* new_value=0);
};
[section:default_constructor `thread_specific_ptr();`]
[variablelist
[[Requires:] [`delete this->get()` is well-formed.]]
[[Effects:] [Construct a `thread_specific_ptr` object for storing a pointer to an object of type `T` specific to each thread. The
default `delete`-based cleanup function will be used to destroy any thread-local objects when `reset()` is called, or the thread
exits.]]
[[Throws:] [`boost::thread_resource_error` if an error occurs.]]
]
[endsect]
[section:constructor_with_custom_cleanup `explicit thread_specific_ptr(void (*cleanup_function)(T*));`]
[variablelist
[[Requires:] [`cleanup_function(this->get())` does not throw any exceptions.]]
[[Effects:] [Construct a `thread_specific_ptr` object for storing a pointer to an object of type `T` specific to each thread. The
supplied `cleanup_function` will be used to destroy any thread-local objects when `reset()` is called, or the thread exits.]]
[[Throws:] [`boost::thread_resource_error` if an error occurs.]]
]
[endsect]
[section:destructor `~thread_specific_ptr();`]
[variablelist
[[Effects:] [Calls `this->reset()` to clean up the associated value for the current thread, and destroys `*this`.]]
[[Throws:] [Nothing.]]
]
[note Care needs to be taken to ensure that any threads still running after an instance of `boost::thread_specific_ptr` has been
destroyed do not call any member functions on that instance.]
[endsect]
[section:get `T* get() const;`]
[variablelist
[[Returns:] [The pointer associated with the current thread.]]
[[Throws:] [Nothing.]]
]
[note The initial value associated with an instance of `boost::thread_specific_ptr` is `NULL` for each thread.]
[endsect]
[section:operator_arrow `T* operator->() const;`]
[variablelist
[[Returns:] [`this->get()`]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:operator_star `T& operator*() const;`]
[variablelist
[[Requires:] [`this->get` is not `NULL`.]]
[[Returns:] [`*(this->get())`]]
[[Throws:] [Nothing.]]
]
[endsect]
[section:reset `void reset(T* new_value=0);`]
[variablelist
[[Effects:] [If `this->get()!=new_value` and `this->get()` is non-`NULL`, invoke `delete this->get()` or
`cleanup_function(this->get())` as appropriate. Store `new_value` as the pointer associated with the current thread.]]
[[Postcondition:] [`this->get()==new_value`]]
[[Throws:] [`boost::thread_resource_error` if an error occurs.]]
]
[endsect]
[section:release `T* release();`]
[variablelist
[[Effects:] [Return `this->get()` and store `NULL` as the pointer associated with the current thread without invoking the cleanup
function.]]
[[Postcondition:] [`this->get()==0`]]
[[Throws:] [Nothing.]]
]
[endsect]
[endsect]
[endsect]

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@@ -1,82 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % thread.entities SYSTEM "entities.xml">
%thread.entities;
]>
<!-- Copyright (c) 2002-2003 William E. Kempf, Michael Glassford
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
-->
<header name="boost/thread/xtime.hpp"
last-revision="$Date$">
<namespace name="boost">
<enum name="xtime_clock_types">
<enumvalue name="TIME_UTC" />
<purpose>
<para>Specifies the clock type to use when creating
an object of type <classname>xtime</classname>.</para>
</purpose>
<description>
<para>The only clock type supported by &Boost.Thread; is
<code>TIME_UTC</code>. The epoch for <code>TIME_UTC</code>
is 1970-01-01 00:00:00.</para>
</description>
</enum>
<struct name="xtime">
<purpose>
<simpara>An object of type <classname>xtime</classname>
defines a time that is used to perform high-resolution time operations.
This is a temporary solution that will be replaced by a more robust time
library once available in Boost.</simpara>
</purpose>
<description>
<simpara>The <classname>xtime</classname> type is used to represent a point on
some time scale or a duration in time. This type may be proposed for the C standard by
Markus Kuhn. &Boost.Thread; provides only a very minimal implementation of this
proposal; it is expected that a full implementation (or some other time
library) will be provided in Boost as a separate library, at which time &Boost.Thread;
will deprecate its own implementation.</simpara>
<simpara><emphasis role="bold">Note</emphasis> that the resolution is
implementation specific. For many implementations the best resolution
of time is far more than one nanosecond, and even when the resolution
is reasonably good, the latency of a call to <code>xtime_get()</code>
may be significant. For maximum portability, avoid durations of less than
one second.</simpara>
</description>
<free-function-group name="creation">
<function name="xtime_get">
<type>int</type>
<parameter name="xtp">
<paramtype><classname>xtime</classname>*</paramtype>
</parameter>
<parameter name="clock_type">
<paramtype>int</paramtype>
</parameter>
<postconditions>
<simpara><code>xtp</code> represents the current point in
time as a duration since the epoch specified by
<code>clock_type</code>.</simpara>
</postconditions>
<returns>
<simpara><code>clock_type</code> if successful, otherwise 0.</simpara>
</returns>
</function>
</free-function-group>
<data-member name="sec">
<type><emphasis>platform-specific-type</emphasis></type>
</data-member>
</struct>
</namespace>
</header>

141
doc/xtime.html Normal file
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@@ -0,0 +1,141 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, Boost.Threads, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, xtime</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">xtime</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Reference">Reference</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>xtime</code> type is used to represent a point on some time scale or
a duration in time. This type may be proposed for the C standard by Markus Kuhn.
<b>Boost.Threads</b> provides only a very minimal implementation of this proposal
and it's expected that a full implementation will be provided in Boost as a separate
library, at which time <b>Boost.Threads</b> will deprecate its implementation.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/xtime.hpp">&lt;boost/thread/xtime.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
enum
{
TIME_UTC=1,
};
struct xtime
{
#if defined(BOOST_NO_INT64_T)
int_fast32_t sec;
#else
int_fast64_t sec;
#endif
int_fast32_t nsec;
};
int xtime_get(struct xtime* xtp, int clock_type);
} // namespace boost
</pre>
<h2><a name="Reference">Reference</a></h2>
<hr>
<h3>TIME_UTC</h3>
<p>The clock type for Coordinated Universal Time (UTC). The epoch for this clock type
is 1970-01-01 00:00:00. This is the only clock type supported by <b>Boost.Threads</b>.</p>
<hr>
<h3>xtime</h3>
<pre>
struct xtime
{
#if defined(BOOST_NO_INT64_T)
int_fast32_t sec;
#else
int_fast64_t sec;
#endif
int_fast32_t nsec;
};
</pre>
<p><b>sec</b> represents the whole seconds that have passed since the epoch.</p>
<p><b>nsec</b> represents the nanoseconds since <code>sec.</code>
<hr>
<h3>xtime_get</h3>
<pre>
int xtime_get(struct xtime* xtp, int clock_type);
</pre>
<p><b>Postcondition:</b> <code>xtp</code> represents the current point in time
as a duration since the epoch specified by the <code>clock_type</code>.</p>
<p><b>Returns:</b> <code>clock_type</code> if successful, otherwise 0.
<p><b>Notes:</b> The resolution is implementation specific. For many
implementations the best resolution of time is far more than one nanosecond, and
even when the resolution is reasonably good, the latency of a call to <code>xtime_get()</code>
may be significant. For maximum portability, avoid durations of less than
one second.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/xtime.hpp&gt;</a>
int main(int argc, char* argv[])
{
boost::xtime xt;
boost::xtime_get(&amp;xt, boost::TIME_UTC);
xt.sec += 1;
boost::thread::sleep(xt); // Sleep for 1 second
}
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->10 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39328" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -1,2 +0,0 @@
bin
*.pdb

66
example/Jamfile Normal file
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@@ -0,0 +1,66 @@
# (C) Copyright William E. Kempf 2001. Permission to copy, use, modify, sell and
# distribute this software is granted provided this copyright notice appears
# in all copies. This software is provided "as is" without express or implied
# warranty, and with no claim as to its suitability for any purpose.
#
# Boost.Threads build and test Jamfile
#
# Declares the following targets:
# 1. monitor, an example program.
# 2. starvephil, an example program.
# 3. tennis, an example program.
# declare the location of this subproject relative to the root
subproject libs/thread/example ;
# Do some OS-specific setup
if $(NT)
{
BOOST_THREADMON_LIB = <lib>../build/libboost_threadmon ;
}
else
{
BOOST_THREADMON_LIB = ;
}
#######################
#
# Declare the Boost.Threads monitor example program.
#
exe monitor : monitor/monitor.cpp
<lib>../build/libboost_thread
$(BOOST_THREADMON_LIB)
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;
#######################
#
# Declare the Boost.Threads starvephil example program.
#
exe starvephil : starvephil/starvephil.cpp
<lib>../build/libboost_thread
$(BOOST_THREADMON_LIB)
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;
#######################
#
# Declare the Boost.Threads tennis example program.
#
exe tennis : tennis/tennis.cpp
<lib>../build/libboost_thread
$(BOOST_THREADMON_LIB)
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;

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@@ -1,23 +0,0 @@
# Copyright (C) 2001-2003
# William E. Kempf
#
# Distributed under the Boost Software License, Version 1.0. (See accompanying
# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
project boost/thread/example
: requirements <library>../build//boost_thread <threading>multi
;
exe monitor : monitor.cpp ;
exe starvephil : starvephil.cpp ;
exe tennis : tennis.cpp ;
exe condition : condition.cpp ;
exe mutex : mutex.cpp ;
exe once : once.cpp ;
exe recursive_mutex : recursive_mutex.cpp ;
exe thread : thread.cpp ;
exe thread_group : thread_group.cpp ;
exe tss : tss.cpp ;
exe xtime : xtime.cpp ;

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@@ -1,82 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <iostream>
#include <vector>
#include <boost/utility.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
class bounded_buffer : private boost::noncopyable
{
public:
typedef boost::mutex::scoped_lock lock;
bounded_buffer(int n) : begin(0), end(0), buffered(0), circular_buf(n) { }
void send (int m) {
lock lk(monitor);
while (buffered == circular_buf.size())
buffer_not_full.wait(lk);
circular_buf[end] = m;
end = (end+1) % circular_buf.size();
++buffered;
buffer_not_empty.notify_one();
}
int receive() {
lock lk(monitor);
while (buffered == 0)
buffer_not_empty.wait(lk);
int i = circular_buf[begin];
begin = (begin+1) % circular_buf.size();
--buffered;
buffer_not_full.notify_one();
return i;
}
private:
int begin, end, buffered;
std::vector<int> circular_buf;
boost::condition buffer_not_full, buffer_not_empty;
boost::mutex monitor;
};
bounded_buffer buf(2);
boost::mutex io_mutex;
void sender() {
int n = 0;
while (n < 100) {
buf.send(n);
{
boost::mutex::scoped_lock io_lock(io_mutex);
std::cout << "sent: " << n << std::endl;
}
++n;
}
buf.send(-1);
}
void receiver() {
int n;
do {
n = buf.receive();
{
boost::mutex::scoped_lock io_lock(io_mutex);
std::cout << "received: " << n << std::endl;
}
} while (n != -1); // -1 indicates end of buffer
}
int main(int, char*[])
{
boost::thread thrd1(&sender);
boost::thread thrd2(&receiver);
thrd1.join();
thrd2.join();
return 0;
}

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@@ -1,9 +1,3 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <vector>
#include <iostream>
#include <boost/thread/condition.hpp>
@@ -12,21 +6,21 @@
#include <boost/thread/thread.hpp>
namespace {
const int ITERS = 100;
boost::mutex io_mutex;
} // namespace
const int ITERS = 100;
boost::mutex io_mutex;
};
template <typename M>
class buffer_t
{
public:
typedef typename M::scoped_lock scoped_lock;
buffer_t(int n)
: p(0), c(0), full(0), buf(n)
{
}
void send(int m)
{
scoped_lock lk(mutex);
@@ -35,7 +29,7 @@ public:
buf[p] = m;
p = (p+1) % buf.size();
++full;
cond.notify_one();
cond.notify_all();
}
int receive()
{
@@ -45,40 +39,41 @@ public:
int i = buf[c];
c = (c+1) % buf.size();
--full;
cond.notify_one();
cond.notify_all();
return i;
}
static buffer_t& get_buffer()
{
static buffer_t buf(2);
return buf;
}
static void do_sender_thread()
{
for (int n = 0; n < ITERS; ++n)
{
get_buffer().send(n);
{
boost::mutex::scoped_lock lock(io_mutex);
std::cout << "sending: " << n << std::endl;
std::cout << "sent: " << n << std::endl;
}
get_buffer().send(n);
}
}
static void do_receiver_thread()
{
for (int x=0; x < (ITERS/2); ++x)
int n;
do
{
int n = get_buffer().receive();
n = get_buffer().receive();
{
boost::mutex::scoped_lock lock(io_mutex);
std::cout << "received: " << n << std::endl;
}
}
} while (n < ITERS - 1);
}
private:
M mutex;
boost::condition cond;
@@ -91,12 +86,10 @@ void do_test(M* dummy=0)
{
typedef buffer_t<M> buffer_type;
buffer_type::get_buffer();
boost::thread thrd1(&buffer_type::do_receiver_thread);
boost::thread thrd1(&buffer_type::do_sender_thread);
boost::thread thrd2(&buffer_type::do_receiver_thread);
boost::thread thrd3(&buffer_type::do_sender_thread);
thrd1.join();
thrd2.join();
thrd3.join();
}
void test_buffer()

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@@ -1,47 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <iostream>
boost::mutex io_mutex; // The iostreams are not guaranteed to be thread-safe!
class counter
{
public:
counter() : count(0) { }
int increment() {
boost::mutex::scoped_lock scoped_lock(mutex);
return ++count;
}
private:
boost::mutex mutex;
int count;
};
counter c;
void change_count()
{
int i = c.increment();
boost::mutex::scoped_lock scoped_lock(io_mutex);
std::cout << "count == " << i << std::endl;
}
int main(int, char*[])
{
const int num_threads = 4;
boost::thread_group thrds;
for (int i=0; i < num_threads; ++i)
thrds.create_thread(&change_count);
thrds.join_all();
return 0;
}

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@@ -1,31 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/thread.hpp>
#include <boost/thread/once.hpp>
#include <cassert>
int value=0;
boost::once_flag once = BOOST_ONCE_INIT;
void init()
{
++value;
}
void thread_proc()
{
boost::call_once(&init, once);
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i<5; ++i)
threads.create_thread(&thread_proc);
threads.join_all();
assert(value == 1);
}

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@@ -1,49 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/recursive_mutex.hpp>
#include <boost/thread/thread.hpp>
#include <iostream>
class counter
{
public:
counter() : count(0) { }
int add(int val) {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
count += val;
return count;
}
int increment() {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
return add(1);
}
private:
boost::recursive_mutex mutex;
int count;
};
counter c;
void change_count()
{
std::cout << "count == " << c.increment() << std::endl;
}
int main(int, char*[])
{
const int num_threads=4;
boost::thread_group threads;
for (int i=0; i < num_threads; ++i)
threads.create_thread(&change_count);
threads.join_all();
return 0;
}

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@@ -1,185 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
#include <time.h>
namespace
{
boost::mutex iomx;
} // namespace
class canteen
{
public:
canteen() : m_chickens(0) { }
void get(int id)
{
boost::mutex::scoped_lock lock(m_mutex);
while (m_chickens == 0)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": wot, no chickens? I'll WAIT ..." << std::endl;
}
m_condition.wait(lock);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": those chickens look good ... one please ..." << std::endl;
}
m_chickens--;
}
void put(int value)
{
boost::mutex::scoped_lock lock(m_mutex);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock()
<< ") Chef: ouch ... make room ... this dish is "
<< "very hot ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
m_chickens += value;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: more chickens ... " << m_chickens <<
" now available ... NOTIFYING ..." << std::endl;
}
m_condition.notify_all();
}
private:
boost::mutex m_mutex;
boost::condition m_condition;
int m_chickens;
};
canteen g_canteen;
void chef()
{
const int chickens = 4;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: starting ..." << std::endl;
}
for (;;)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: cooking ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 2;
boost::thread::sleep(xt);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: " << chickens
<< " chickens, ready-to-go ..." << std::endl;
}
g_canteen.put(chickens);
}
}
struct phil
{
phil(int id) : m_id(id) { }
void run() {
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": starting ..." << std::endl;
}
for (;;)
{
if (m_id > 0)
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": gotta eat ..." << std::endl;
}
g_canteen.get(m_id);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": mmm ... that's good ..." << std::endl;
}
}
}
static void do_thread(void* param) {
static_cast<phil*>(param)->run();
}
int m_id;
};
struct thread_adapt
{
thread_adapt(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
int operator()() const
{
_func(_param);
return 0;
}
void (*_func)(void*);
void* _param;
};
class thread_adapter
{
public:
thread_adapter(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
void operator()() const { _func(_param); }
private:
void (*_func)(void*);
void* _param;
};
int main(int argc, char* argv[])
{
boost::thread thrd_chef(&chef);
phil p[] = { phil(0), phil(1), phil(2), phil(3), phil(4) };
boost::thread thrd_phil0(thread_adapter(&phil::do_thread, &p[0]));
boost::thread thrd_phil1(thread_adapter(&phil::do_thread, &p[1]));
boost::thread thrd_phil2(thread_adapter(&phil::do_thread, &p[2]));
boost::thread thrd_phil3(thread_adapter(&phil::do_thread, &p[3]));
boost::thread thrd_phil4(thread_adapter(&phil::do_thread, &p[4]));
thrd_chef.join();
thrd_phil0.join();
thrd_phil1.join();
thrd_phil2.join();
thrd_phil3.join();
thrd_phil4.join();
return 0;
}

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@@ -0,0 +1,171 @@
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
#include <time.h>
namespace
{
boost::mutex iomx;
};
class canteen
{
public:
canteen() : m_chickens(0) { }
void get(int id)
{
boost::mutex::scoped_lock lock(m_mutex);
while (m_chickens == 0)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": wot, no chickens? I'll WAIT ..." << std::endl;
}
m_condition.wait(lock);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": those chickens look good ... one please ..." << std::endl;
}
m_chickens--;
}
void put(int value)
{
boost::mutex::scoped_lock lock(m_mutex);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: ouch ... make room ... this dish is very hot ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
m_chickens += value;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: more chickens ... " << m_chickens <<
" now available ... NOTIFYING ..." << std::endl;
}
m_condition.notify_all();
}
private:
boost::mutex m_mutex;
boost::condition m_condition;
int m_chickens;
};
canteen g_canteen;
void chef()
{
const int chickens = 4;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: starting ..." << std::endl;
}
for (;;)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: cooking ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 2;
boost::thread::sleep(xt);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: " << chickens
<< " chickens, ready-to-go ..." << std::endl;
}
g_canteen.put(chickens);
}
}
struct phil
{
phil(int id) : m_id(id) { }
void run() {
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id << ": starting ..." << std::endl;
}
for (;;)
{
if (m_id > 0)
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": gotta eat ..." << std::endl;
}
g_canteen.get(m_id);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": mmm ... that's good ..." << std::endl;
}
}
}
static void do_thread(void* param) {
static_cast<phil*>(param)->run();
}
int m_id;
};
struct thread_adapt
{
thread_adapt(void (*func)(void*), void* param) : _func(func), _param(param) { }
int operator()() const
{
_func(_param);
return 0;
}
void (*_func)(void*);
void* _param;
};
class thread_adapter
{
public:
thread_adapter(void (*func)(void*), void* param) : _func(func), _param(param) { }
void operator()() const { _func(_param); }
private:
void (*_func)(void*);
void* _param;
};
int main(int argc, char* argv[])
{
boost::thread thrd_chef(&chef);
phil p[] = { phil(0), phil(1), phil(2), phil(3), phil(4) };
boost::thread thrd_phil0(thread_adapter(&phil::do_thread, &p[0]));
boost::thread thrd_phil1(thread_adapter(&phil::do_thread, &p[1]));
boost::thread thrd_phil2(thread_adapter(&phil::do_thread, &p[2]));
boost::thread thrd_phil3(thread_adapter(&phil::do_thread, &p[3]));
boost::thread thrd_phil4(thread_adapter(&phil::do_thread, &p[4]));
thrd_chef.join();
thrd_phil0.join();
thrd_phil1.join();
thrd_phil2.join();
thrd_phil3.join();
thrd_phil4.join();
return 0;
}

View File

@@ -1,18 +1,13 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/semaphore.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
#if defined(BOOST_HAS_WINTHREADS)
# include <windows.h>
# include <process.h>
# include <windows.h>
# include <process.h>
#endif
enum game_state
@@ -55,10 +50,7 @@ void player(void* param)
{
cond.wait(lock);
if (state == other)
{
std::cout << "---" << player_name(active)
<< ": Spurious wakeup!" << std::endl;
}
std::cout << "---" << player_name(active) << ": Spurious wakeup!" << std::endl;
} while (state == other);
}
@@ -69,10 +61,7 @@ void player(void* param)
struct thread_adapt
{
thread_adapt(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
thread_adapt(void (*func)(void*), void* param) : _func(func), _param(param) { }
int operator()() const
{
_func(_param);
@@ -86,10 +75,7 @@ struct thread_adapt
class thread_adapter
{
public:
thread_adapter(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
thread_adapter(void (*func)(void*), void* param) : _func(func), _param(param) { }
void operator()() const { _func(_param); }
private:
void (*_func)(void*);

View File

@@ -1,35 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
struct thread_alarm
{
thread_alarm(int secs) : m_secs(secs) { }
void operator()()
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += m_secs;
boost::thread::sleep(xt);
std::cout << "alarm sounded..." << std::endl;
}
int m_secs;
};
int main(int argc, char* argv[])
{
int secs = 5;
std::cout << "setting alarm for 5 seconds..." << std::endl;
thread_alarm alarm(secs);
boost::thread thrd(alarm);
thrd.join();
}

View File

@@ -1,25 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/thread.hpp>
#include <iostream>
int count = 0;
boost::mutex mutex;
void increment_count()
{
boost::mutex::scoped_lock lock(mutex);
std::cout << "count = " << ++count << std::endl;
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i = 0; i < 10; ++i)
threads.create_thread(&increment_count);
threads.join_all();
}

View File

@@ -1,36 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/thread.hpp>
#include <boost/thread/tss.hpp>
#include <cassert>
boost::thread_specific_ptr<int> value;
void increment()
{
int* p = value.get();
++*p;
}
void thread_proc()
{
value.reset(new int(0)); // initialize the thread's storage
for (int i=0; i<10; ++i)
{
increment();
int* p = value.get();
assert(*p == i+1);
}
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i<5; ++i)
threads.create_thread(&thread_proc);
threads.join_all();
}

View File

@@ -1,16 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
int main(int argc, char* argv[])
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 1;
boost::thread::sleep(xt); // Sleep for 1 second
}

View File

@@ -1,25 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
// (C) Copyright 2008 Anthony Williams
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
// See www.boost.org/libs/thread for documentation.
#if !defined(BOOST_THREAD_WEK01082003_HPP)
#define BOOST_THREAD_WEK01082003_HPP
#include <boost/thread/thread.hpp>
#include <boost/thread/condition_variable.hpp>
#include <boost/thread/exceptions.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/once.hpp>
#include <boost/thread/recursive_mutex.hpp>
#include <boost/thread/tss.hpp>
#include <boost/thread/thread_time.hpp>
#include <boost/thread/locks.hpp>
#include <boost/thread/shared_mutex.hpp>
#include <boost/thread/barrier.hpp>
#endif

View File

@@ -0,0 +1,61 @@
/*
*
* Copyright (C) 2001
* William E. Kempf
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. William E. Kempf makes no representations
* about the suitability of this software for any purpose.
* It is provided "as is" without express or implied warranty.
*
* Revision History (excluding minor changes for specific compilers)
* 8 Feb 01 Initial version.
*/
#ifndef BOOST_ATOMIC_HPP
#define BOOST_ATOMIC_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#if !defined(BOOST_HAS_WINTHREADS)
# include <boost/thread/mutex.hpp>
#endif
namespace boost {
class atomic_t
{
public:
typedef long value_type;
friend value_type read(const atomic_t&);
friend value_type increment(atomic_t&);
friend value_type decrement(atomic_t&);
friend value_type swap(atomic_t&, value_type);
friend value_type compare_swap(atomic_t&, value_type, value_type);
explicit atomic_t(value_type val=0)
: _value(val)
{
}
private:
volatile value_type _value;
#if !defined(BOOST_HAS_WINTHREADS)
mutex _mutex;
#endif
};
extern atomic_t::value_type read(const atomic_t&);
extern atomic_t::value_type increment(atomic_t&);
extern atomic_t::value_type decrement(atomic_t&);
extern atomic_t::value_type swap(atomic_t&, atomic_t::value_type);
extern atomic_t::value_type compare_swap(atomic_t&, atomic_t::value_type, atomic_t::value_type);
} // namespace boost
#endif // BOOST_ATOMIC_HPP

View File

@@ -1,63 +0,0 @@
// Copyright (C) 2002-2003
// David Moore, William E. Kempf
// Copyright (C) 2007-8 Anthony Williams
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_BARRIER_JDM030602_HPP
#define BOOST_BARRIER_JDM030602_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition_variable.hpp>
#include <string>
#include <stdexcept>
#include <boost/config/abi_prefix.hpp>
namespace boost
{
class barrier
{
public:
barrier(unsigned int count)
: m_threshold(count), m_count(count), m_generation(0)
{
if (count == 0)
throw std::invalid_argument("count cannot be zero.");
}
bool wait()
{
boost::mutex::scoped_lock lock(m_mutex);
unsigned int gen = m_generation;
if (--m_count == 0)
{
m_generation++;
m_count = m_threshold;
m_cond.notify_all();
return true;
}
while (gen == m_generation)
m_cond.wait(lock);
return false;
}
private:
mutex m_mutex;
condition_variable m_cond;
unsigned int m_threshold;
unsigned int m_count;
unsigned int m_generation;
};
} // namespace boost
#include <boost/config/abi_suffix.hpp>
#endif

View File

@@ -1,16 +1,156 @@
#ifndef BOOST_THREAD_CONDITION_HPP
#define BOOST_THREAD_CONDITION_HPP
// (C) Copyright 2007 Anthony Williams
// Copyright (C) 2001
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/condition_variable.hpp>
namespace boost
{
typedef condition_variable_any condition;
}
#ifndef BOOST_CONDITION_WEK070601_HPP
#define BOOST_CONDITION_WEK070601_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/thread/exceptions.hpp>
#include <boost/utility.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
#endif
namespace boost {
struct xtime;
class condition : private noncopyable
{
public:
condition();
~condition();
void notify_one();
void notify_all();
template <typename L>
void wait(L& lock)
{
if (!lock)
throw lock_error();
do_wait(lock.m_mutex);
}
template <typename L, typename Pr>
void wait(L& lock, Pr pred)
{
if (!lock)
throw lock_error();
while (!pred())
do_wait(lock.m_mutex);
}
template <typename L>
bool timed_wait(L& lock, const xtime& xt)
{
if (!lock)
throw lock_error();
return do_timed_wait(lock.m_mutex, xt);
}
template <typename L, typename Pr>
bool timed_wait(L& lock, const xtime& xt, Pr pred)
{
if (!lock)
throw lock_error();
while (!pred())
{
if (!do_timed_wait(lock.m_mutex, xt))
return false;
}
return true;
}
private:
template <typename M>
void do_wait(M& mutex)
{
#if defined(BOOST_HAS_WINTHREADS)
enter_wait();
#endif
typename M::cv_state state;
mutex.do_unlock(state);
#if defined(BOOST_HAS_PTHREADS)
do_wait(state.pmutex);
#elif defined(BOOST_HAS_WINTHREADS)
do_wait();
#endif
mutex.do_lock(state);
}
template <typename M>
bool do_timed_wait(M& mutex, const xtime& xt)
{
#if defined(BOOST_HAS_WINTHREADS)
enter_wait();
#endif
typename M::cv_state state;
mutex.do_unlock(state);
bool ret = false;
#if defined(BOOST_HAS_PTHREADS)
ret = do_timed_wait(xt, state.pmutex);
#elif defined(BOOST_HAS_WINTHREADS)
ret = do_timed_wait(xt);
#endif
mutex.do_lock(state);
return ret;
}
#if defined(BOOST_HAS_WINTHREADS)
void enter_wait();
void do_wait();
bool do_timed_wait(const xtime& xt);
#elif defined(BOOST_HAS_PTHREADS)
void do_wait(pthread_mutex_t* pmutex);
bool do_timed_wait(const xtime& xt, pthread_mutex_t* pmutex);
#endif
#if defined(BOOST_HAS_WINTHREADS)
unsigned long m_gate;
unsigned long m_queue;
unsigned long m_mutex;
unsigned m_gone; // # threads that timed out and never made it to the m_queue
unsigned long m_blocked; // # threads m_blocked m_waiting for the condition
unsigned m_waiting; // # threads m_waiting no longer m_waiting for the condition but still
// m_waiting to be removed from the m_queue
#elif defined(BOOST_HAS_PTHREADS)
pthread_cond_t m_condition;
#endif
};
} // namespace boost
// Change Log:
// 8 Feb 01 WEKEMPF Initial version.
// 22 May 01 WEKEMPF Modified to use xtime for time outs.
// 23 May 01 WEKEMPF Removed "duration" timed_waits, as they are too difficult
// to use with spurious wakeups.
#endif // BOOST_CONDITION_WEK070601_HPP

View File

@@ -1,21 +0,0 @@
#ifndef BOOST_THREAD_CONDITION_VARIABLE_HPP
#define BOOST_THREAD_CONDITION_VARIABLE_HPP
// condition_variable.hpp
//
// (C) Copyright 2007 Anthony Williams
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/detail/platform.hpp>
#if defined(BOOST_THREAD_PLATFORM_WIN32)
#include <boost/thread/win32/condition_variable.hpp>
#elif defined(BOOST_THREAD_PLATFORM_PTHREAD)
#include <boost/thread/pthread/condition_variable.hpp>
#else
#error "Boost threads unavailable on this platform"
#endif
#endif

View File

@@ -0,0 +1,100 @@
// Copyright (C) 2001
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
// This file is used to configure Boost.Threads during development
// in order to decouple dependency on any Boost release. Once
// accepted into Boost these contents will be moved to <boost/config>
// or some other appropriate build configuration and all
// #include <boost/thread/config.hpp> statements will be changed
// accordingly.
#ifndef BOOST_THREAD_CONFIG_WEK070601_HPP
#define BOOST_THREAD_CONFIG_WEK070601_HPP
#include <boost/config.hpp>
#error "Included <boost/thread/config.hpp>"
/*// Define if threading support is enabled for the toolset.
#undef BOOST_HAS_THREADS
// Define if threading should be implemented in terms of Win32 threads.
#undef BOOST_HAS_WINTHREADS
// Define if threading should be implemented in terms of POSIX threads.
#undef BOOST_HAS_PTHREADS
// Define if BOOST_HAS_PTHREADS and pthread_delay_np() exists.
#undef BOOST_HAS_PTHREAD_DELAY_NP
// Define if BOOST_HAS_PTHREADS and not BOOST_HAS_PTHREAD_DELAY_NP
// but nanosleep can be used instead.
#undef BOOST_HAS_NANOSLEEP
// Define if BOOST_HAS_PTHREADS and pthread_yield() exists.
#undef BOOST_HAS_PTHREAD_YIELD
// Define if BOOST_HAS_PTHREADS and not BOOST_HAS_PTHREAD_YIELD and
// sched_yield() exists.
#undef BOOST_HAS_SCHED_YIELD
// Define if gettimeofday() exists.
#undef BOOST_HAS_GETTIMEOFDAY
// Define if not BOOST_HAS_GETTIMEOFDAY and clock_gettime() exists.
#undef BOOST_HAS_CLOCK_GETTIME
// Define if not BOOST_HAS_GETTIMEOFDAY and not BOOST_HAS_CLOCK_GETTIME and
// GetSystemTimeAsFileTime() can be called with an FTIME structure.
#undef BOOST_HAS_FTIME
// Define if pthread_mutexattr_settype and pthread_mutexattr_gettype exist.
#undef BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
// Here we'll set up known compiler options.
#if defined(BOOST_MSVC)
# if defined(_MT)
# define BOOST_HAS_THREADS
# endif
# define BOOST_HAS_WINTHREADS // comment out this to test pthreads-win32.
# if !defined(BOOST_HAS_WINTHREADS)
# define BOOST_HAS_PTHREADS
# define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
# define PtW32NoCatchWarn
# pragma comment(lib, "pthreadVCE.lib")
# endif
# define BOOST_HAS_FTIME
// pdm: this is for linux - is there a better #define to #if on?
// wek: not sure how else to do this, but GNU CC on Win32 should probably
// use BOOST_HAS_WINTHREADS, and I expect there will be other
// platform specific variations for this compiler toolset. Need
// to decide how to handle this.
#elif defined( __GNUC__ )
# define BOOST_HAS_THREADS
# define BOOST_HAS_PTHREADS
# define BOOST_HAS_NANOSLEEP
# define BOOST_HAS_GETTIMEOFDAY
// pdm: From the pthread.h header, one of these macros
// must be defined for this stuff to exist.
// wek: This seems like a harmless enough method to determine these
// switches, but one should note that some implementations may not
// use these. Notably, pthreads-win32 doesn't define either
// __USE_UNIX98 or __USE_GNU.
# if defined( __USE_UNIX98 )
# define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
# elif defined( __USE_GNU )
# define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
# define BOOST_HAS_PTHREAD_YIELD
# endif
#endif*/
#endif // BOOST_THREAD_CONFIG_WEK070601_HPP

View File

@@ -1,94 +0,0 @@
// Copyright (C) 2001-2003
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_THREAD_CONFIG_WEK01032003_HPP
#define BOOST_THREAD_CONFIG_WEK01032003_HPP
#include <boost/config.hpp>
#include <boost/detail/workaround.hpp>
#if BOOST_WORKAROUND(__BORLANDC__, < 0x600)
# pragma warn -8008 // Condition always true/false
# pragma warn -8080 // Identifier declared but never used
# pragma warn -8057 // Parameter never used
# pragma warn -8066 // Unreachable code
#endif
#include "platform.hpp"
// compatibility with the rest of Boost's auto-linking code:
#if defined(BOOST_THREAD_DYN_DLL) || defined(BOOST_ALL_DYN_LINK)
# undef BOOST_THREAD_USE_LIB
# define BOOST_THREAD_USE_DLL
#endif
#if defined(BOOST_THREAD_BUILD_DLL) //Build dll
#elif defined(BOOST_THREAD_BUILD_LIB) //Build lib
#elif defined(BOOST_THREAD_USE_DLL) //Use dll
#elif defined(BOOST_THREAD_USE_LIB) //Use lib
#else //Use default
# if defined(BOOST_THREAD_PLATFORM_WIN32)
# if defined(BOOST_MSVC) || defined(BOOST_INTEL_WIN)
//For compilers supporting auto-tss cleanup
//with Boost.Threads lib, use Boost.Threads lib
# define BOOST_THREAD_USE_LIB
# else
//For compilers not yet supporting auto-tss cleanup
//with Boost.Threads lib, use Boost.Threads dll
# define BOOST_THREAD_USE_DLL
# endif
# else
# define BOOST_THREAD_USE_LIB
# endif
#endif
#if defined(BOOST_HAS_DECLSPEC)
# if defined(BOOST_THREAD_BUILD_DLL) //Build dll
# define BOOST_THREAD_DECL __declspec(dllexport)
# elif defined(BOOST_THREAD_USE_DLL) //Use dll
# define BOOST_THREAD_DECL __declspec(dllimport)
# else
# define BOOST_THREAD_DECL
# endif
#else
# define BOOST_THREAD_DECL
#endif // BOOST_HAS_DECLSPEC
//
// Automatically link to the correct build variant where possible.
//
#if !defined(BOOST_ALL_NO_LIB) && !defined(BOOST_THREAD_NO_LIB) && !defined(BOOST_THREAD_BUILD_DLL) && !defined(BOOST_THREAD_BUILD_LIB)
//
// Tell the autolink to link dynamically, this will get undef'ed by auto_link.hpp
// once it's done with it:
//
#if defined(BOOST_THREAD_USE_DLL)
# define BOOST_DYN_LINK
#endif
//
// Set the name of our library, this will get undef'ed by auto_link.hpp
// once it's done with it:
//
#if defined(BOOST_THREAD_LIB_NAME)
# define BOOST_LIB_NAME BOOST_THREAD_LIB_NAME
#else
# define BOOST_LIB_NAME boost_thread
#endif
//
// If we're importing code from a dll, then tell auto_link.hpp about it:
//
// And include the header that does the work:
//
#include <boost/config/auto_link.hpp>
#endif // auto-linking disabled
#endif // BOOST_THREAD_CONFIG_WEK1032003_HPP
// Change Log:
// 22 Jan 05 Roland Schwarz (speedsnail)
// Usage of BOOST_HAS_DECLSPEC macro.
// Default again is static lib usage.
// BOOST_DYN_LINK only defined when autolink included.

View File

@@ -1,39 +0,0 @@
// Copyright (C) 2001-2003
// Mac Murrett
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_FORCE_CAST_MJM012402_HPP
#define BOOST_FORCE_CAST_MJM012402_HPP
#include <boost/thread/detail/config.hpp>
namespace boost {
namespace detail {
namespace thread {
// force_cast will convert anything to anything.
// general case
template<class Return_Type, class Argument_Type>
inline Return_Type &force_cast(Argument_Type &rSrc)
{
return(*reinterpret_cast<Return_Type *>(&rSrc));
}
// specialization for const
template<class Return_Type, class Argument_Type>
inline const Return_Type &force_cast(const Argument_Type &rSrc)
{
return(*reinterpret_cast<const Return_Type *>(&rSrc));
}
} // namespace thread
} // namespace detail
} // namespace boost
#endif // BOOST_FORCE_CAST_MJM012402_HPP

View File

@@ -1,14 +1,17 @@
// Copyright (C) 2001-2003
// Copyright (C) 2001
// William E. Kempf
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_XLOCK_WEK070601_HPP
#define BOOST_XLOCK_WEK070601_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/thread/exceptions.hpp>
@@ -17,193 +20,153 @@ namespace boost {
class condition;
struct xtime;
namespace detail { namespace thread {
namespace detail { namespace thread {
template <typename Mutex>
class lock_ops : private noncopyable
{
private:
lock_ops() { }
template <typename Mutex>
class scoped_lock : private noncopyable
{
public:
typedef Mutex mutex_type;
explicit scoped_lock(Mutex& mx, bool initially_locked=true)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
m_mutex.do_lock();
m_locked = true;
}
void unlock()
{
if (!m_locked) throw lock_error();
m_mutex.do_unlock();
m_locked = false;
}
public:
typedef typename Mutex::cv_state lock_state;
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
Mutex& m_mutex;
bool m_locked;
};
static void lock(Mutex& m)
template <typename TryMutex>
class scoped_try_lock : private noncopyable
{
m.do_lock();
}
static bool trylock(Mutex& m)
{
return m.do_trylock();
}
static bool timedlock(Mutex& m, const xtime& xt)
{
return m.do_timedlock(xt);
}
static void unlock(Mutex& m)
{
m.do_unlock();
}
static void lock(Mutex& m, lock_state& state)
{
m.do_lock(state);
}
static void unlock(Mutex& m, lock_state& state)
{
m.do_unlock(state);
}
};
public:
typedef TryMutex mutex_type;
explicit scoped_try_lock(TryMutex& mx)
: m_mutex(mx), m_locked(false)
{
try_lock();
}
scoped_try_lock(TryMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_try_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
m_mutex.do_lock();
m_locked = true;
}
bool try_lock()
{
if (m_locked) throw lock_error();
return (m_locked = m_mutex.do_trylock());
}
void unlock()
{
if (!m_locked) throw lock_error();
m_mutex.do_unlock();
m_locked = false;
}
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
TryMutex& m_mutex;
bool m_locked;
};
template <typename Mutex>
class scoped_lock : private noncopyable
{
public:
typedef Mutex mutex_type;
explicit scoped_lock(Mutex& mx, bool initially_locked=true)
: m_mutex(mx), m_locked(false)
template <typename TimedMutex>
class scoped_timed_lock : private noncopyable
{
if (initially_locked) lock();
}
~scoped_lock()
{
if (m_locked) unlock();
}
public:
typedef TimedMutex mutex_type;
scoped_timed_lock(TimedMutex& mx, const xtime& xt)
: m_mutex(mx), m_locked(false)
{
timed_lock(xt);
}
scoped_timed_lock(TimedMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_timed_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
m_mutex.do_lock();
m_locked = true;
}
bool timed_lock(const xtime& xt)
{
if (m_locked) throw lock_error();
return (m_locked = m_mutex.do_timedlock(xt));
}
void unlock()
{
if (!m_locked) throw lock_error();
m_mutex.do_unlock();
m_locked = false;
}
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
TimedMutex& m_mutex;
bool m_locked;
};
void lock()
{
if (m_locked) throw lock_error();
lock_ops<Mutex>::lock(m_mutex);
m_locked = true;
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<Mutex>::unlock(m_mutex);
m_locked = false;
}
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
Mutex& m_mutex;
bool m_locked;
};
template <typename TryMutex>
class scoped_try_lock : private noncopyable
{
public:
typedef TryMutex mutex_type;
explicit scoped_try_lock(TryMutex& mx)
: m_mutex(mx), m_locked(false)
{
try_lock();
}
scoped_try_lock(TryMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_try_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TryMutex>::lock(m_mutex);
m_locked = true;
}
bool try_lock()
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TryMutex>::trylock(m_mutex));
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TryMutex>::unlock(m_mutex);
m_locked = false;
}
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
TryMutex& m_mutex;
bool m_locked;
};
template <typename TimedMutex>
class scoped_timed_lock : private noncopyable
{
public:
typedef TimedMutex mutex_type;
scoped_timed_lock(TimedMutex& mx, const xtime& xt)
: m_mutex(mx), m_locked(false)
{
timed_lock(xt);
}
scoped_timed_lock(TimedMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_timed_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TimedMutex>::lock(m_mutex);
m_locked = true;
}
bool try_lock()
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TimedMutex>::trylock(m_mutex));
}
bool timed_lock(const xtime& xt)
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TimedMutex>::timedlock(m_mutex, xt));
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TimedMutex>::unlock(m_mutex);
m_locked = false;
}
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
TimedMutex& m_mutex;
bool m_locked;
};
} // namespace thread
} // namespace detail
} // namespace thread
} // namespace detail
} // namespace boost
#endif // BOOST_XLOCK_WEK070601_HPP
// Change Log:
// 8 Feb 01 WEKEMPF Initial version.
// 22 May 01 WEKEMPF Modified to use xtime for time outs.
// 30 Jul 01 WEKEMPF Moved lock types into boost::detail::thread. Renamed
// some types. Added locked() methods.
// 30 Jul 01 WEKEMPF Moved lock types into boost::detail::thread. Renamed some types.
// Added locked() methods.
#endif // BOOST_XLOCK_WEK070601_HPP

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// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// (C) Copyright 2007-8 Anthony Williams
#ifndef BOOST_THREAD_MOVE_HPP
#define BOOST_THREAD_MOVE_HPP
#ifndef BOOST_NO_SFINAE
#include <boost/utility/enable_if.hpp>
#include <boost/type_traits/is_convertible.hpp>
#endif
#include <boost/config/abi_prefix.hpp>
namespace boost
{
namespace detail
{
template<typename T>
struct thread_move_t
{
T& t;
explicit thread_move_t(T& t_):
t(t_)
{}
T& operator*() const
{
return t;
}
T* operator->() const
{
return &t;
}
private:
void operator=(thread_move_t&);
};
}
#ifndef BOOST_NO_SFINAE
template<typename T>
typename enable_if<boost::is_convertible<T&,detail::thread_move_t<T> >, T >::type move(T& t)
{
return T(detail::thread_move_t<T>(t));
}
#endif
template<typename T>
detail::thread_move_t<T> move(detail::thread_move_t<T> t)
{
return t;
}
}
#include <boost/config/abi_suffix.hpp>
#endif

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// Copyright 2006 Roland Schwarz.
// (C) Copyright 2007 Anthony Williams
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// This work is a reimplementation along the design and ideas
// of William E. Kempf.
#ifndef BOOST_THREAD_RS06040501_HPP
#define BOOST_THREAD_RS06040501_HPP
// fetch compiler and platform configuration
#include <boost/config.hpp>
// insist on threading support being available:
#include <boost/config/requires_threads.hpp>
// choose platform
#if defined(linux) || defined(__linux) || defined(__linux__)
# define BOOST_THREAD_LINUX
#elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__)
# define BOOST_THREAD_BSD
#elif defined(sun) || defined(__sun)
# define BOOST_THREAD_SOLARIS
#elif defined(__sgi)
# define BOOST_THREAD_IRIX
#elif defined(__hpux)
# define BOOST_THREAD_HPUX
#elif defined(__CYGWIN__)
# define BOOST_THREAD_CYGWIN
#elif defined(_WIN32) || defined(__WIN32__) || defined(WIN32)
# define BOOST_THREAD_WIN32
#elif defined(__BEOS__)
# define BOOST_THREAD_BEOS
#elif defined(macintosh) || defined(__APPLE__) || defined(__APPLE_CC__)
# define BOOST_THREAD_MACOS
#elif defined(__IBMCPP__) || defined(_AIX)
# define BOOST_THREAD_AIX
#elif defined(__amigaos__)
# define BOOST_THREAD_AMIGAOS
#elif defined(__QNXNTO__)
# define BOOST_THREAD_QNXNTO
#elif defined(unix) || defined(__unix) || defined(_XOPEN_SOURCE) || defined(_POSIX_SOURCE)
# if defined(BOOST_HAS_PTHREADS) && !defined(BOOST_THREAD_POSIX)
# define BOOST_THREAD_POSIX
# endif
#endif
// For every supported platform add a new entry into the dispatch table below.
// BOOST_THREAD_POSIX is tested first, so on platforms where posix and native
// threading is available, the user may choose, by defining BOOST_THREAD_POSIX
// in her source. If a platform is known to support pthreads and no native
// port of boost_thread is available just specify "pthread" in the
// dispatcher table. If there is no entry for a platform but pthreads is
// available on the platform, pthread is choosen as default. If nothing is
// available the preprocessor will fail with a diagnostic message.
#if defined(BOOST_THREAD_POSIX)
# define BOOST_THREAD_PLATFORM_PTHREAD
#else
# if defined(BOOST_THREAD_WIN32)
# define BOOST_THREAD_PLATFORM_WIN32
# elif defined(BOOST_HAS_PTHREADS)
# define BOOST_THREAD_PLATFORM_PTHREAD
# else
# error "Sorry, no boost threads are available for this platform."
# endif
#endif
#endif // BOOST_THREAD_RS06040501_HPP

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// Copyright (C) 2001-2003
// Mac Murrett
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_SINGLETON_MJM012402_HPP
#define BOOST_SINGLETON_MJM012402_HPP
#include <boost/thread/detail/config.hpp>
namespace boost {
namespace detail {
namespace thread {
// class singleton has the same goal as all singletons: create one instance of
// a class on demand, then dish it out as requested.
template <class T>
class singleton : private T
{
private:
singleton();
~singleton();
public:
static T &instance();
};
template <class T>
inline singleton<T>::singleton()
{
/* no-op */
}
template <class T>
inline singleton<T>::~singleton()
{
/* no-op */
}
template <class T>
/*static*/ T &singleton<T>::instance()
{
// function-local static to force this to work correctly at static
// initialization time.
static singleton<T> s_oT;
return(s_oT);
}
} // namespace thread
} // namespace detail
} // namespace boost
#endif // BOOST_SINGLETON_MJM012402_HPP

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#ifndef BOOST_THREAD_THREAD_COMMON_HPP
#define BOOST_THREAD_THREAD_COMMON_HPP
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// (C) Copyright 2007-8 Anthony Williams
#include <boost/thread/exceptions.hpp>
#include <ostream>
#include <boost/thread/detail/move.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/xtime.hpp>
#include <boost/thread/detail/thread_heap_alloc.hpp>
#include <boost/utility.hpp>
#include <boost/assert.hpp>
#include <list>
#include <algorithm>
#include <boost/ref.hpp>
#include <boost/cstdint.hpp>
#include <boost/bind.hpp>
#include <stdlib.h>
#include <memory>
#include <boost/utility/enable_if.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/config/abi_prefix.hpp>
#ifdef BOOST_MSVC
#pragma warning(push)
#pragma warning(disable:4251)
#endif
namespace boost
{
namespace detail
{
template<typename F>
class thread_data:
public detail::thread_data_base
{
public:
#ifdef BOOST_HAS_RVALUE_REFS
thread_data(F&& f_):
f(static_cast<F&&>(f_))
{}
#else
thread_data(F f_):
f(f_)
{}
thread_data(detail::thread_move_t<F> f_):
f(f_)
{}
#endif
void run()
{
f();
}
private:
F f;
void operator=(thread_data&);
thread_data(thread_data&);
};
template<typename F>
class thread_data<boost::reference_wrapper<F> >:
public detail::thread_data_base
{
private:
F& f;
void operator=(thread_data&);
thread_data(thread_data&);
public:
thread_data(boost::reference_wrapper<F> f_):
f(f_)
{}
void run()
{
f();
}
};
template<typename F>
class thread_data<const boost::reference_wrapper<F> >:
public detail::thread_data_base
{
private:
F& f;
void operator=(thread_data&);
thread_data(thread_data&);
public:
thread_data(const boost::reference_wrapper<F> f_):
f(f_)
{}
void run()
{
f();
}
};
}
class BOOST_THREAD_DECL thread
{
private:
thread(thread&);
thread& operator=(thread&);
void release_handle();
mutable boost::mutex thread_info_mutex;
detail::thread_data_ptr thread_info;
void start_thread();
explicit thread(detail::thread_data_ptr data);
detail::thread_data_ptr get_thread_info() const;
#ifdef BOOST_HAS_RVALUE_REFS
template<typename F>
static inline detail::thread_data_ptr make_thread_info(F&& f)
{
return detail::thread_data_ptr(detail::heap_new<detail::thread_data<typename boost::remove_reference<F>::type> >(static_cast<F&&>(f)));
}
static inline detail::thread_data_ptr make_thread_info(void (*f)())
{
return detail::thread_data_ptr(detail::heap_new<detail::thread_data<void(*)()> >(f));
}
#else
template<typename F>
static inline detail::thread_data_ptr make_thread_info(F f)
{
return detail::thread_data_ptr(detail::heap_new<detail::thread_data<F> >(f));
}
template<typename F>
static inline detail::thread_data_ptr make_thread_info(boost::detail::thread_move_t<F> f)
{
return detail::thread_data_ptr(detail::heap_new<detail::thread_data<F> >(f));
}
struct dummy;
#endif
public:
thread();
~thread();
#ifdef BOOST_HAS_RVALUE_REFS
template <class F>
thread(F&& f):
thread_info(make_thread_info(static_cast<F&&>(f)))
{
start_thread();
}
thread(thread&& other)
{
thread_info.swap(other.thread_info);
}
thread& operator=(thread&& other)
{
thread_info=other.thread_info;
other.thread_info.reset();
return *this;
}
thread&& move()
{
return static_cast<thread&&>(*this);
}
#else
#ifdef BOOST_NO_SFINAE
template <class F>
explicit thread(F f):
thread_info(make_thread_info(f))
{
start_thread();
}
#else
template <class F>
explicit thread(F f,typename disable_if<boost::is_convertible<F&,detail::thread_move_t<F> >, dummy* >::type=0):
thread_info(make_thread_info(f))
{
start_thread();
}
#endif
template <class F>
explicit thread(detail::thread_move_t<F> f):
thread_info(make_thread_info(f))
{
start_thread();
}
thread(detail::thread_move_t<thread> x)
{
thread_info=x->thread_info;
x->thread_info.reset();
}
thread& operator=(detail::thread_move_t<thread> x)
{
thread new_thread(x);
swap(new_thread);
return *this;
}
operator detail::thread_move_t<thread>()
{
return move();
}
detail::thread_move_t<thread> move()
{
detail::thread_move_t<thread> x(*this);
return x;
}
#endif
template <class F,class A1>
thread(F f,A1 a1):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1)))
{
start_thread();
}
template <class F,class A1,class A2>
thread(F f,A1 a1,A2 a2):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2)))
{
start_thread();
}
template <class F,class A1,class A2,class A3>
thread(F f,A1 a1,A2 a2,A3 a3):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2,a3)))
{
start_thread();
}
template <class F,class A1,class A2,class A3,class A4>
thread(F f,A1 a1,A2 a2,A3 a3,A4 a4):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2,a3,a4)))
{
start_thread();
}
template <class F,class A1,class A2,class A3,class A4,class A5>
thread(F f,A1 a1,A2 a2,A3 a3,A4 a4,A5 a5):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2,a3,a4,a5)))
{
start_thread();
}
template <class F,class A1,class A2,class A3,class A4,class A5,class A6>
thread(F f,A1 a1,A2 a2,A3 a3,A4 a4,A5 a5,A6 a6):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2,a3,a4,a5,a6)))
{
start_thread();
}
template <class F,class A1,class A2,class A3,class A4,class A5,class A6,class A7>
thread(F f,A1 a1,A2 a2,A3 a3,A4 a4,A5 a5,A6 a6,A7 a7):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2,a3,a4,a5,a6,a7)))
{
start_thread();
}
template <class F,class A1,class A2,class A3,class A4,class A5,class A6,class A7,class A8>
thread(F f,A1 a1,A2 a2,A3 a3,A4 a4,A5 a5,A6 a6,A7 a7,A8 a8):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2,a3,a4,a5,a6,a7,a8)))
{
start_thread();
}
template <class F,class A1,class A2,class A3,class A4,class A5,class A6,class A7,class A8,class A9>
thread(F f,A1 a1,A2 a2,A3 a3,A4 a4,A5 a5,A6 a6,A7 a7,A8 a8,A9 a9):
thread_info(make_thread_info(boost::bind(boost::type<void>(),f,a1,a2,a3,a4,a5,a6,a7,a8,a9)))
{
start_thread();
}
void swap(thread& x)
{
thread_info.swap(x.thread_info);
}
class id;
id get_id() const;
bool joinable() const;
void join();
bool timed_join(const system_time& wait_until);
template<typename TimeDuration>
inline bool timed_join(TimeDuration const& rel_time)
{
return timed_join(get_system_time()+rel_time);
}
void detach();
static unsigned hardware_concurrency();
typedef detail::thread_data_base::native_handle_type native_handle_type;
native_handle_type native_handle();
// backwards compatibility
bool operator==(const thread& other) const;
bool operator!=(const thread& other) const;
static inline void yield()
{
this_thread::yield();
}
static inline void sleep(const system_time& xt)
{
this_thread::sleep(xt);
}
// extensions
void interrupt();
bool interruption_requested() const;
};
inline void swap(thread& lhs,thread& rhs)
{
return lhs.swap(rhs);
}
#ifdef BOOST_HAS_RVALUE_REFS
inline thread&& move(thread&& t)
{
return t;
}
#else
inline thread move(detail::thread_move_t<thread> t)
{
return thread(t);
}
#endif
namespace this_thread
{
class BOOST_THREAD_DECL disable_interruption
{
disable_interruption(const disable_interruption&);
disable_interruption& operator=(const disable_interruption&);
bool interruption_was_enabled;
friend class restore_interruption;
public:
disable_interruption();
~disable_interruption();
};
class BOOST_THREAD_DECL restore_interruption
{
restore_interruption(const restore_interruption&);
restore_interruption& operator=(const restore_interruption&);
public:
explicit restore_interruption(disable_interruption& d);
~restore_interruption();
};
thread::id BOOST_THREAD_DECL get_id();
void BOOST_THREAD_DECL interruption_point();
bool BOOST_THREAD_DECL interruption_enabled();
bool BOOST_THREAD_DECL interruption_requested();
inline void sleep(xtime const& abs_time)
{
sleep(system_time(abs_time));
}
}
class thread::id
{
private:
detail::thread_data_ptr thread_data;
id(detail::thread_data_ptr thread_data_):
thread_data(thread_data_)
{}
friend class thread;
friend id this_thread::get_id();
public:
id():
thread_data()
{}
bool operator==(const id& y) const
{
return thread_data==y.thread_data;
}
bool operator!=(const id& y) const
{
return thread_data!=y.thread_data;
}
bool operator<(const id& y) const
{
return thread_data<y.thread_data;
}
bool operator>(const id& y) const
{
return y.thread_data<thread_data;
}
bool operator<=(const id& y) const
{
return !(y.thread_data<thread_data);
}
bool operator>=(const id& y) const
{
return !(thread_data<y.thread_data);
}
template<class charT, class traits>
friend std::basic_ostream<charT, traits>&
operator<<(std::basic_ostream<charT, traits>& os, const id& x)
{
if(x.thread_data)
{
return os<<x.thread_data;
}
else
{
return os<<"{Not-any-thread}";
}
}
};
inline bool thread::operator==(const thread& other) const
{
return get_id()==other.get_id();
}
inline bool thread::operator!=(const thread& other) const
{
return get_id()!=other.get_id();
}
namespace detail
{
struct thread_exit_function_base
{
virtual ~thread_exit_function_base()
{}
virtual void operator()() const=0;
};
template<typename F>
struct thread_exit_function:
thread_exit_function_base
{
F f;
thread_exit_function(F f_):
f(f_)
{}
void operator()() const
{
f();
}
};
void add_thread_exit_function(thread_exit_function_base*);
}
namespace this_thread
{
template<typename F>
void at_thread_exit(F f)
{
detail::thread_exit_function_base* const thread_exit_func=detail::heap_new<detail::thread_exit_function<F> >(f);
detail::add_thread_exit_function(thread_exit_func);
}
}
class thread_group:
private noncopyable
{
public:
~thread_group()
{
for(std::list<thread*>::iterator it=threads.begin(),end=threads.end();
it!=end;
++it)
{
delete *it;
}
}
template<typename F>
thread* create_thread(F threadfunc)
{
boost::lock_guard<mutex> guard(m);
std::auto_ptr<thread> new_thread(new thread(threadfunc));
threads.push_back(new_thread.get());
return new_thread.release();
}
void add_thread(thread* thrd)
{
if(thrd)
{
boost::lock_guard<mutex> guard(m);
threads.push_back(thrd);
}
}
void remove_thread(thread* thrd)
{
boost::lock_guard<mutex> guard(m);
std::list<thread*>::iterator const it=std::find(threads.begin(),threads.end(),thrd);
if(it!=threads.end())
{
threads.erase(it);
}
}
void join_all()
{
boost::lock_guard<mutex> guard(m);
for(std::list<thread*>::iterator it=threads.begin(),end=threads.end();
it!=end;
++it)
{
(*it)->join();
}
}
void interrupt_all()
{
boost::lock_guard<mutex> guard(m);
for(std::list<thread*>::iterator it=threads.begin(),end=threads.end();
it!=end;
++it)
{
(*it)->interrupt();
}
}
size_t size() const
{
boost::lock_guard<mutex> guard(m);
return threads.size();
}
private:
std::list<thread*> threads;
mutable mutex m;
};
}
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
#include <boost/config/abi_suffix.hpp>
#endif

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@@ -1,23 +0,0 @@
#ifndef BOOST_THREAD_THREAD_HEAP_ALLOC_HPP
#define BOOST_THREAD_THREAD_HEAP_ALLOC_HPP
// thread_heap_alloc.hpp
//
// (C) Copyright 2008 Anthony Williams
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#include <boost/thread/detail/platform.hpp>
#if defined(BOOST_THREAD_PLATFORM_WIN32)
#include <boost/thread/win32/thread_heap_alloc.hpp>
#elif defined(BOOST_THREAD_PLATFORM_PTHREAD)
#include <boost/thread/pthread/thread_heap_alloc.hpp>
#else
#error "Boost threads unavailable on this platform"
#endif
#endif

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@@ -1,82 +0,0 @@
// (C) Copyright Michael Glassford 2004.
// Use, modification and distribution are subject to the
// Boost Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#if !defined(BOOST_TLS_HOOKS_HPP)
#define BOOST_TLS_HOOKS_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/config/abi_prefix.hpp>
#if defined(BOOST_HAS_WINTHREADS)
typedef void (__cdecl *thread_exit_handler)(void);
extern "C" BOOST_THREAD_DECL int at_thread_exit(
thread_exit_handler exit_handler
);
//Add a function to the list of functions that will
//be called when a thread is about to exit.
//Currently only implemented for Win32, but should
//later be implemented for all platforms.
//Used by Win32 implementation of Boost.Threads
//tss to perform cleanup.
//Like the C runtime library atexit() function,
//which it mimics, at_thread_exit() returns
//zero if successful and a nonzero
//value if an error occurs.
#endif //defined(BOOST_HAS_WINTHREADS)
#if defined(BOOST_HAS_WINTHREADS)
extern "C" BOOST_THREAD_DECL void on_process_enter(void);
//Function to be called when the exe or dll
//that uses Boost.Threads first starts
//or is first loaded.
//Should be called only before the first call to
//on_thread_enter().
//Called automatically by Boost.Threads when
//a method for doing so has been discovered.
//May be omitted; may be called multiple times.
extern "C" BOOST_THREAD_DECL void on_process_exit(void);
//Function to be called when the exe or dll
//that uses Boost.Threads first starts
//or is first loaded.
//Should be called only after the last call to
//on_exit_thread().
//Called automatically by Boost.Threads when
//a method for doing so has been discovered.
//Must not be omitted; may be called multiple times.
extern "C" BOOST_THREAD_DECL void on_thread_enter(void);
//Function to be called just after a thread starts
//in an exe or dll that uses Boost.Threads.
//Must be called in the context of the thread
//that is starting.
//Called automatically by Boost.Threads when
//a method for doing so has been discovered.
//May be omitted; may be called multiple times.
extern "C" BOOST_THREAD_DECL void __cdecl on_thread_exit(void);
//Function to be called just be fore a thread ends
//in an exe or dll that uses Boost.Threads.
//Must be called in the context of the thread
//that is ending.
//Called automatically by Boost.Threads when
//a method for doing so has been discovered.
//Must not be omitted; may be called multiple times.
extern "C" void tss_cleanup_implemented(void);
//Dummy function used both to detect whether tss cleanup
//cleanup has been implemented and to force
//it to be linked into the Boost.Threads library.
#endif //defined(BOOST_HAS_WINTHREADS)
#include <boost/config/abi_suffix.hpp>
#endif //!defined(BOOST_TLS_HOOKS_HPP)

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