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108 lines
3.4 KiB
C++
108 lines
3.4 KiB
C++
// (C) Copyright 2013 Andrey Semashev
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// (C) Copyright 2013 Vicente J. Botet Escriba
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#define __STDC_CONSTANT_MACROS
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#include <boost/thread/detail/config.hpp>
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#include <boost/thread/once.hpp>
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#include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp>
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#include <boost/assert.hpp>
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#include <boost/static_assert.hpp>
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#include <boost/atomic.hpp>
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#include <boost/memory_order.hpp>
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#include <pthread.h>
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namespace boost
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{
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namespace thread_detail
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{
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enum flag_states
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{
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uninitialized, in_progress, initialized
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};
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#if BOOST_ATOMIC_INT_LOCK_FREE == 2
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typedef unsigned int atomic_int_type;
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#elif BOOST_ATOMIC_SHORT_LOCK_FREE == 2
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typedef unsigned short atomic_int_type;
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#elif BOOST_ATOMIC_CHAR_LOCK_FREE == 2
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typedef unsigned char atomic_int_type;
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#elif BOOST_ATOMIC_LONG_LOCK_FREE == 2
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typedef unsigned long atomic_int_type;
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#elif defined(BOOST_HAS_LONG_LONG) && BOOST_ATOMIC_LLONG_LOCK_FREE == 2
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typedef ulong_long_type atomic_int_type;
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#else
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// All tested integer types are not atomic, the spinlock pool will be used
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typedef unsigned int atomic_int_type;
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#endif
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typedef boost::atomic<atomic_int_type> atomic_type
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//#if defined(__GNUC__)
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// __attribute__((may_alias))
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//#endif
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;
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BOOST_STATIC_ASSERT_MSG(sizeof(once_flag) >= sizeof(atomic_type), "Boost.Thread: unsupported platform");
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static pthread_mutex_t once_mutex = PTHREAD_MUTEX_INITIALIZER;
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static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER;
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BOOST_THREAD_DECL bool enter_once_region(once_flag& flag) BOOST_NOEXCEPT
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{
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atomic_type& f = reinterpret_cast< atomic_type& >(flag.storage);
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if (f.load(memory_order_acquire) != initialized)
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{
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pthread::pthread_mutex_scoped_lock lk(&once_mutex);
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if (f.load(memory_order_acquire) != initialized)
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{
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while (true)
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{
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atomic_int_type expected = uninitialized;
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if (f.compare_exchange_strong(expected, in_progress, memory_order_acq_rel, memory_order_acquire))
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{
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// We have set the flag to in_progress
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return true;
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}
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else if (expected == initialized)
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{
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// Another thread managed to complete the initialization
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return false;
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}
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else
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{
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// Wait until the initialization is complete
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//pthread::pthread_mutex_scoped_lock lk(&once_mutex);
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BOOST_VERIFY(!pthread_cond_wait(&once_cv, &once_mutex));
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}
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}
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}
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}
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return false;
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}
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BOOST_THREAD_DECL void commit_once_region(once_flag& flag) BOOST_NOEXCEPT
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{
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atomic_type& f = reinterpret_cast< atomic_type& >(flag.storage);
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{
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pthread::pthread_mutex_scoped_lock lk(&once_mutex);
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f.store(initialized, memory_order_release);
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}
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BOOST_VERIFY(!pthread_cond_broadcast(&once_cv));
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}
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BOOST_THREAD_DECL void rollback_once_region(once_flag& flag) BOOST_NOEXCEPT
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{
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atomic_type& f = reinterpret_cast< atomic_type& >(flag.storage);
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{
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pthread::pthread_mutex_scoped_lock lk(&once_mutex);
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f.store(uninitialized, memory_order_release);
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}
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BOOST_VERIFY(!pthread_cond_broadcast(&once_cv));
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}
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} // namespace thread_detail
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} // namespace boost
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