| #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP |
| #define BOOST_THREAD_PTHREAD_ONCE_HPP |
| |
| // once.hpp |
| // |
| // (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) |
| |
| #include <boost/thread/detail/config.hpp> |
| #include <boost/config.hpp> |
| |
| #include <pthread.h> |
| #include <boost/assert.hpp> |
| #include "pthread_mutex_scoped_lock.hpp" |
| #include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp> |
| #include <boost/cstdint.hpp> |
| |
| #include <boost/config/abi_prefix.hpp> |
| |
| namespace boost |
| { |
| |
| struct once_flag |
| { |
| boost::uintmax_t epoch; |
| }; |
| |
| namespace detail |
| { |
| BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); |
| BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; |
| BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; |
| BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; |
| } |
| |
| #define BOOST_ONCE_INITIAL_FLAG_VALUE 0 |
| #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} |
| |
| |
| // Based on Mike Burrows fast_pthread_once algorithm as described in |
| // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html |
| template<typename Function> |
| void call_once(once_flag& flag,Function f) |
| { |
| static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; |
| static boost::uintmax_t const being_initialized=uninitialized_flag+1; |
| boost::uintmax_t const epoch=flag.epoch; |
| boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); |
| |
| if(epoch<this_thread_epoch) |
| { |
| pthread::pthread_mutex_scoped_lock lk(&detail::once_epoch_mutex); |
| |
| while(flag.epoch<=being_initialized) |
| { |
| if(flag.epoch==uninitialized_flag) |
| { |
| flag.epoch=being_initialized; |
| #ifndef BOOST_NO_EXCEPTIONS |
| try |
| { |
| #endif |
| pthread::pthread_mutex_scoped_unlock relocker(&detail::once_epoch_mutex); |
| f(); |
| #ifndef BOOST_NO_EXCEPTIONS |
| } |
| catch(...) |
| { |
| flag.epoch=uninitialized_flag; |
| BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv)); |
| throw; |
| } |
| #endif |
| flag.epoch=--detail::once_global_epoch; |
| BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv)); |
| } |
| else |
| { |
| while(flag.epoch==being_initialized) |
| { |
| BOOST_VERIFY(!pthread_cond_wait(&detail::once_epoch_cv,&detail::once_epoch_mutex)); |
| } |
| } |
| } |
| this_thread_epoch=detail::once_global_epoch; |
| } |
| } |
| } |
| |
| #include <boost/config/abi_suffix.hpp> |
| |
| #endif |