#include <boost/thread/detail/config.hpp>

#include <boost/thread/once.hpp>

#include <boost/thread/pthread/pthread_helpers.hpp>

#include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp>

#include <boost/assert.hpp>

#include <boost/static_assert.hpp>

#include <boost/atomic.hpp>

#include <boost/memory_order.hpp>

#include <pthread.h>

namespace boost

{

namespace thread_detail

{

enum flag_states

{

uninitialized, in_progress, initialized

};

#ifndef BOOST_THREAD_PROVIDES_ONCE_CXX11

BOOST_STATIC_ASSERT_MSG(sizeof(atomic_int_type) == sizeof(atomic_type), "Boost.Thread: unsupported platform");

#endif

static pthread_mutex_t once_mutex = PTHREAD_MUTEX_INITIALIZER;

static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER;

BOOST_THREAD_DECL bool enter_once_region(once_flag& flag) BOOST_NOEXCEPT

{

atomic_type& f = get_atomic_storage(flag);

if (f.load(memory_order_acquire) != initialized)

{

pthread::pthread_mutex_scoped_lock lk(&once_mutex);

if (f.load(memory_order_acquire) != initialized)

{

for (;;)

{

atomic_int_type expected = uninitialized;

if (f.compare_exchange_strong(expected, in_progress, memory_order_acq_rel, memory_order_acquire))

{

// We have set the flag to in_progress

return true;

}

else if (expected == initialized)

{

// Another thread managed to complete the initialization

return false;

}

else

{

// Wait until the initialization is complete

//pthread::pthread_mutex_scoped_lock lk(&once_mutex);

BOOST_VERIFY(!posix::pthread_cond_wait(&once_cv, &once_mutex));

}

}

}

}

return false;

}

BOOST_THREAD_DECL void commit_once_region(once_flag& flag) BOOST_NOEXCEPT

{

atomic_type& f = get_atomic_storage(flag);

{

pthread::pthread_mutex_scoped_lock lk(&once_mutex);

f.store(initialized, memory_order_release);

}

BOOST_VERIFY(!posix::pthread_cond_broadcast(&once_cv));

}

BOOST_THREAD_DECL void rollback_once_region(once_flag& flag) BOOST_NOEXCEPT

{

atomic_type& f = get_atomic_storage(flag);

{

pthread::pthread_mutex_scoped_lock lk(&once_mutex);

f.store(uninitialized, memory_order_release);

}

BOOST_VERIFY(!posix::pthread_cond_broadcast(&once_cv));

}

} // namespace thread_detail

} // namespace boost