First Commit

externals/boost/libs/thread/src/pthread/once_atomic.cpp

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+//  (C) Copyright 2013 Andrey Semashev
+//  (C) Copyright 2013 Vicente J. Botet Escriba
+//
+//  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)
+
+//#define __STDC_CONSTANT_MACROS
+#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