Add support for using an eventfd descriptor on linux to interrupt a blocked

epoll/select reactor.


[SVN r48524]

include/boost/asio/detail/eventfd_select_interrupter.hpp

@@ -0,0 +1,124 @@
+//
+// eventfd_select_interrupter.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2008 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+// Copyright (c) 2008 Roelof Naude (roelof.naude at gmail dot com)
+//
+// 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_ASIO_DETAIL_EVENTFD_SELECT_INTERRUPTER_HPP
+#define BOOST_ASIO_DETAIL_EVENTFD_SELECT_INTERRUPTER_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <boost/asio/detail/push_options.hpp>
+
+#include <boost/asio/detail/push_options.hpp>
+#include <boost/config.hpp>
+#include <boost/throw_exception.hpp>
+#include <boost/system/system_error.hpp>
+#include <boost/asio/detail/pop_options.hpp>
+
+#if defined(linux)
+# if !defined(BOOST_ASIO_DISABLE_EVENTFD)
+#  include <linux/version.h>
+#  if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
+#   define BOOST_ASIO_HAS_EVENTFD
+#  endif // LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
+# endif // !defined(BOOST_ASIO_DISABLE_EVENTFD)
+#endif // defined(linux)
+
+#if defined(BOOST_ASIO_HAS_EVENTFD)
+
+#include <boost/asio/detail/push_options.hpp>
+#include <fcntl.h>
+#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
+# include <asm/unistd.h>
+#else // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
+# include <sys/eventfd.h>
+#endif // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
+#include <boost/asio/detail/pop_options.hpp>
+
+#include <boost/asio/error.hpp>
+#include <boost/asio/detail/socket_types.hpp>
+
+namespace boost {
+namespace asio {
+namespace detail {
+
+class eventfd_select_interrupter
+{
+public:
+  // Constructor.
+  eventfd_select_interrupter()
+  {
+#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
+    read_descriptor_ = syscall(__NR_eventfd, 0);
+#else // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
+    read_descriptor_ = ::eventfd(0, 0);
+#endif // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
+    if (read_descriptor_ != -1)
+    {
+      ::fcntl(read_descriptor_, F_SETFL, O_NONBLOCK);
+    }
+    else
+    {
+      boost::system::error_code ec(errno,
+          boost::asio::error::get_system_category());
+      boost::system::system_error e(ec, "eventfd_select_interrupter");
+      boost::throw_exception(e);
+    }
+  }
+
+  // Destructor.
+  ~eventfd_select_interrupter()
+  {
+    if (read_descriptor_ != -1)
+      ::close(read_descriptor_);
+  }
+
+  // Interrupt the select call.
+  void interrupt()
+  {
+    uint64_t counter(1UL);
+    ::write(read_descriptor_, &counter, sizeof(uint64_t));
+  }
+
+  // Reset the select interrupt. Returns true if the call was interrupted.
+  bool reset()
+  {
+    // Only perform one read. The kernel maintains an atomic counter.
+    uint64_t counter(0);
+    int bytes_read = ::read(read_descriptor_, &counter, sizeof(uint64_t));
+    bool was_interrupted = (bytes_read > 0);
+    return was_interrupted;
+  }
+
+  // Get the read descriptor to be passed to select.
+  int read_descriptor() const
+  {
+    return read_descriptor_;
+  }
+
+private:
+  // The read end of a connection used to interrupt the select call. This file
+  // descriptor is passed to select such that when it is time to stop, a single
+  // 64bit value will be written on the other end of the connection and this
+  // descriptor will become readable.
+  int read_descriptor_;
+};
+
+} // namespace detail
+} // namespace asio
+} // namespace boost
+
+#endif // defined(BOOST_ASIO_HAS_EVENTFD)
+
+#include <boost/asio/detail/pop_options.hpp>
+
+#endif // BOOST_ASIO_DETAIL_EVENTFD_SELECT_INTERRUPTER_HPP

include/boost/asio/detail/select_interrupter.hpp

@@ -21,6 +21,7 @@
 #include <boost/config.hpp>
 #include <boost/asio/detail/pop_options.hpp>
 
+#include <boost/asio/detail/eventfd_select_interrupter.hpp>
 #include <boost/asio/detail/pipe_select_interrupter.hpp>
 #include <boost/asio/detail/socket_select_interrupter.hpp>
 
@@ -30,6 +31,8 @@ namespace detail {
 
 #if defined(BOOST_WINDOWS) || defined(__CYGWIN__)
 typedef socket_select_interrupter select_interrupter;
+#elif defined(BOOST_ASIO_HAS_EVENTFD)
+typedef eventfd_select_interrupter select_interrupter;
 #else
 typedef pipe_select_interrupter select_interrupter;
 #endif