1 #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP
2 #define BOOST_THREAD_PTHREAD_ONCE_HPP
6 // (C) Copyright 2007-8 Anthony Williams
8 // Distributed under the Boost Software License, Version 1.0. (See
9 // accompanying file LICENSE_1_0.txt or copy at
10 // http://www.boost.org/LICENSE_1_0.txt)
12 #include <boost/thread/detail/config.hpp>
13 #include <boost/config.hpp>
16 #include <boost/assert.hpp>
17 #include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp>
18 #include <boost/cstdint.hpp>
20 #include <boost/config/abi_prefix.hpp>
27 boost::uintmax_t epoch;
32 BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch();
33 BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch;
34 BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex;
35 BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv;
38 #define BOOST_ONCE_INITIAL_FLAG_VALUE 0
39 #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE}
42 // Based on Mike Burrows fast_pthread_once algorithm as described in
43 // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html
44 template<typename Function>
45 void call_once(once_flag& flag,Function f)
47 static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE;
48 static boost::uintmax_t const being_initialized=uninitialized_flag+1;
49 boost::uintmax_t const epoch=flag.epoch;
50 boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch();
52 if(epoch<this_thread_epoch)
54 pthread::pthread_mutex_scoped_lock lk(&detail::once_epoch_mutex);
56 while(flag.epoch<=being_initialized)
58 if(flag.epoch==uninitialized_flag)
60 flag.epoch=being_initialized;
61 #ifndef BOOST_NO_EXCEPTIONS
65 pthread::pthread_mutex_scoped_unlock relocker(&detail::once_epoch_mutex);
67 #ifndef BOOST_NO_EXCEPTIONS
71 flag.epoch=uninitialized_flag;
72 BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv));
76 flag.epoch=--detail::once_global_epoch;
77 BOOST_VERIFY(!pthread_cond_broadcast(&detail::once_epoch_cv));
81 while(flag.epoch==being_initialized)
83 BOOST_VERIFY(!pthread_cond_wait(&detail::once_epoch_cv,&detail::once_epoch_mutex));
87 this_thread_epoch=detail::once_global_epoch;
92 #include <boost/config/abi_suffix.hpp>