boost/thread/win32/basic_timed_mutex.hpp
#ifndef BOOST_BASIC_TIMED_MUTEX_WIN32_HPP #define BOOST_BASIC_TIMED_MUTEX_WIN32_HPP // basic_timed_mutex_win32.hpp // // (C) Copyright 2006-8 Anthony Williams // (C) Copyright 2011-2012 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) #include <boost/assert.hpp> #include <boost/thread/win32/thread_primitives.hpp> #include <boost/thread/win32/interlocked_read.hpp> #include <boost/thread/thread_time.hpp> #if defined BOOST_THREAD_USES_DATETIME #include <boost/thread/xtime.hpp> #endif #include <boost/detail/interlocked.hpp> #ifdef BOOST_THREAD_USES_CHRONO #include <boost/chrono/system_clocks.hpp> #include <boost/chrono/ceil.hpp> #endif #include <boost/thread/detail/platform_time.hpp> #include <boost/config/abi_prefix.hpp> namespace boost { namespace detail { struct basic_timed_mutex { BOOST_STATIC_CONSTANT(unsigned char,lock_flag_bit=31); BOOST_STATIC_CONSTANT(unsigned char,event_set_flag_bit=30); BOOST_STATIC_CONSTANT(long,lock_flag_value=1<<lock_flag_bit); BOOST_STATIC_CONSTANT(long,event_set_flag_value=1<<event_set_flag_bit); long active_count; void* event; void initialize() { active_count=0; event=0; } void destroy() { #ifdef BOOST_MSVC #pragma warning(push) #pragma warning(disable:4312) #endif void* const old_event=BOOST_INTERLOCKED_EXCHANGE_POINTER(&event,0); #ifdef BOOST_MSVC #pragma warning(pop) #endif if(old_event) { winapi::CloseHandle(old_event); } } // Take the lock flag if it's available bool try_lock() BOOST_NOEXCEPT { return !win32::interlocked_bit_test_and_set(&active_count,lock_flag_bit); } void lock() { if(try_lock()) { return; } long old_count=active_count; mark_waiting_and_try_lock(old_count); if(old_count&lock_flag_value) { void* const sem=get_event(); do { if(winapi::WaitForSingleObjectEx(sem,::boost::detail::win32::infinite,0)==0) { clear_waiting_and_try_lock(old_count); } } while(old_count&lock_flag_value); } } // Loop until the number of waiters has been incremented or we've taken the lock flag // The loop is necessary since this function may be called by multiple threads simultaneously void mark_waiting_and_try_lock(long& old_count) { for(;;) { bool const was_locked=(old_count&lock_flag_value) ? true : false; long const new_count=was_locked?(old_count+1):(old_count|lock_flag_value); long const current=BOOST_INTERLOCKED_COMPARE_EXCHANGE(&active_count,new_count,old_count); if(current==old_count) { if(was_locked) old_count=new_count; // else we've taken the lock flag // don't update old_count so that the calling function can see that // the old lock flag was 0 and know that we've taken the lock flag break; } old_count=current; } } // Loop until someone else has taken the lock flag and cleared the event set flag or // until we've taken the lock flag and cleared the event set flag and decremented the // number of waiters // The loop is necessary since this function may be called by multiple threads simultaneously void clear_waiting_and_try_lock(long& old_count) { old_count&=~lock_flag_value; old_count|=event_set_flag_value; for(;;) { long const new_count=((old_count&lock_flag_value)?old_count:((old_count-1)|lock_flag_value))&~event_set_flag_value; long const current=BOOST_INTERLOCKED_COMPARE_EXCHANGE(&active_count,new_count,old_count); if(current==old_count) { // if someone else has taken the lock flag // no need to update old_count since old_count == new_count (ignoring // event_set_flag_value which the calling function doesn't care about) // else we've taken the lock flag // don't update old_count so that the calling function can see that // the old lock flag was 0 and know that we've taken the lock flag break; } old_count=current; } } private: unsigned long getMs(detail::platform_duration const& d) { return static_cast<unsigned long>(d.getMs()); } template <typename Duration> unsigned long getMs(Duration const& d) { return static_cast<unsigned long>(chrono::ceil<chrono::milliseconds>(d).count()); } template <typename Clock, typename Timepoint, typename Duration> bool do_lock_until(Timepoint const& t, Duration const& max) { if(try_lock()) { return true; } long old_count=active_count; mark_waiting_and_try_lock(old_count); if(old_count&lock_flag_value) { void* const sem=get_event(); // If the clock is the system clock, it may jump while this function // is waiting. To compensate for this and time out near the correct // time, we call WaitForSingleObjectEx() in a loop with a short // timeout and recheck the time remaining each time through the loop. do { Duration d(t - Clock::now()); if(d <= Duration::zero()) // timeout occurred { BOOST_INTERLOCKED_DECREMENT(&active_count); return false; } if(max != Duration::zero()) { d = (std::min)(d, max); } if(winapi::WaitForSingleObjectEx(sem,getMs(d),0)==0) { clear_waiting_and_try_lock(old_count); } } while(old_count&lock_flag_value); } return true; } public: #if defined BOOST_THREAD_USES_DATETIME bool timed_lock(::boost::system_time const& wait_until) { const detail::real_platform_timepoint t(wait_until); return do_lock_until<detail::real_platform_clock>(t, detail::platform_milliseconds(BOOST_THREAD_POLL_INTERVAL_MILLISECONDS)); } template<typename Duration> bool timed_lock(Duration const& timeout) { const detail::mono_platform_timepoint t(detail::mono_platform_clock::now() + detail::platform_duration(timeout)); // The reference clock is steady and so no need to poll periodically, thus 0 ms max (i.e. no max) return do_lock_until<detail::mono_platform_clock>(t, detail::platform_duration::zero()); } bool timed_lock(boost::xtime const& timeout) { return timed_lock(boost::system_time(timeout)); } #endif #ifdef BOOST_THREAD_USES_CHRONO template <class Rep, class Period> bool try_lock_for(const chrono::duration<Rep, Period>& rel_time) { const chrono::steady_clock::time_point t(chrono::steady_clock::now() + rel_time); typedef typename chrono::duration<Rep, Period> Duration; typedef typename common_type<Duration, typename chrono::steady_clock::duration>::type common_duration; // The reference clock is steady and so no need to poll periodically, thus 0 ms max (i.e. no max) return do_lock_until<chrono::steady_clock>(t, common_duration::zero()); } template <class Duration> bool try_lock_until(const chrono::time_point<chrono::steady_clock, Duration>& t) { typedef typename common_type<Duration, typename chrono::steady_clock::duration>::type common_duration; // The reference clock is steady and so no need to poll periodically, thus 0 ms max (i.e. no max) return do_lock_until<chrono::steady_clock>(t, common_duration::zero()); } template <class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& t) { typedef typename common_type<Duration, typename Clock::duration>::type common_duration; return do_lock_until<Clock>(t, common_duration(chrono::milliseconds(BOOST_THREAD_POLL_INTERVAL_MILLISECONDS))); } #endif void unlock() { // Clear the lock flag using atomic addition (works since long is always 32 bits on Windows) long const old_count=BOOST_INTERLOCKED_EXCHANGE_ADD(&active_count,lock_flag_value); // If someone is waiting to take the lock, set the event set flag and, if // the event set flag hadn't already been set, send an event. if(!(old_count&event_set_flag_value) && (old_count>lock_flag_value)) { if(!win32::interlocked_bit_test_and_set(&active_count,event_set_flag_bit)) { winapi::SetEvent(get_event()); } } } private: // Create an event in a thread-safe way // The first thread to create the event wins and all other thread will use that event void* get_event() { void* current_event=::boost::detail::interlocked_read_acquire(&event); if(!current_event) { void* const new_event=win32::create_anonymous_event(win32::auto_reset_event,win32::event_initially_reset); #ifdef BOOST_MSVC #pragma warning(push) #pragma warning(disable:4311) #pragma warning(disable:4312) #endif void* const old_event=BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER(&event,new_event,0); #ifdef BOOST_MSVC #pragma warning(pop) #endif if(old_event!=0) { winapi::CloseHandle(new_event); return old_event; } else { return new_event; } } return current_event; } }; } } #define BOOST_BASIC_TIMED_MUTEX_INITIALIZER {0} #include <boost/config/abi_suffix.hpp> #endif