/Src/Dependencies/Boost/boost/interprocess/sync/emulation/interprocess_condition.hpp
http://hadesmem.googlecode.com/ · C++ Header · 200 lines · 112 code · 24 blank · 64 comment · 23 complexity · 6351b5287424835a812b2455b2da500c MD5 · raw file
- //////////////////////////////////////////////////////////////////////////////
- //
- // (C) Copyright Ion Gaztanaga 2005-2009. 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)
- //
- // See http://www.boost.org/libs/interprocess for documentation.
- //
- //////////////////////////////////////////////////////////////////////////////
- #include <boost/interprocess/detail/posix_time_types_wrk.hpp>
- #include <boost/interprocess/detail/move.hpp>
- namespace boost {
- namespace interprocess {
- inline interprocess_condition::interprocess_condition()
- {
- //Note that this class is initialized to zero.
- //So zeroed memory can be interpreted as an initialized
- //condition variable
- m_command = SLEEP;
- m_num_waiters = 0;
- }
- inline interprocess_condition::~interprocess_condition()
- {
- //Trivial destructor
- }
- inline void interprocess_condition::notify_one()
- {
- this->notify(NOTIFY_ONE);
- }
- inline void interprocess_condition::notify_all()
- {
- this->notify(NOTIFY_ALL);
- }
- inline void interprocess_condition::notify(boost::uint32_t command)
- {
- //This interprocess_mutex guarantees that no other thread can enter to the
- //do_timed_wait method logic, so that thread count will be
- //constant until the function writes a NOTIFY_ALL command.
- //It also guarantees that no other notification can be signaled
- //on this interprocess_condition before this one ends
- m_enter_mut.lock();
- //Return if there are no waiters
- if(!detail::atomic_read32(&m_num_waiters)) {
- m_enter_mut.unlock();
- return;
- }
- //Notify that all threads should execute wait logic
- while(SLEEP != detail::atomic_cas32(const_cast<boost::uint32_t*>(&m_command), command, SLEEP)){
- detail::thread_yield();
- }
- /*
- //Wait until the threads are woken
- while(SLEEP != detail::atomic_cas32(const_cast<boost::uint32_t*>(&m_command), 0)){
- detail::thread_yield();
- }
- */
- //The enter interprocess_mutex will rest locked until the last waiting thread unlocks it
- }
- inline void interprocess_condition::do_wait(interprocess_mutex &mut)
- {
- this->do_timed_wait(false, boost::posix_time::ptime(), mut);
- }
- inline bool interprocess_condition::do_timed_wait
- (const boost::posix_time::ptime &abs_time, interprocess_mutex &mut)
- {
- return this->do_timed_wait(true, abs_time, mut);
- }
- inline bool interprocess_condition::do_timed_wait(bool tout_enabled,
- const boost::posix_time::ptime &abs_time,
- interprocess_mutex &mut)
- {
- boost::posix_time::ptime now = microsec_clock::universal_time();
-
- if(tout_enabled){
- if(now >= abs_time) return false;
- }
- typedef boost::interprocess::scoped_lock<interprocess_mutex> InternalLock;
- //The enter interprocess_mutex guarantees that while executing a notification,
- //no other thread can execute the do_timed_wait method.
- {
- //---------------------------------------------------------------
- InternalLock lock;
- if(tout_enabled){
- InternalLock dummy(m_enter_mut, abs_time);
- lock = boost::interprocess::move(dummy);
- }
- else{
- InternalLock dummy(m_enter_mut);
- lock = boost::interprocess::move(dummy);
- }
- if(!lock)
- return false;
- //---------------------------------------------------------------
- //We increment the waiting thread count protected so that it will be
- //always constant when another thread enters the notification logic.
- //The increment marks this thread as "waiting on interprocess_condition"
- detail::atomic_inc32(const_cast<boost::uint32_t*>(&m_num_waiters));
- //We unlock the external interprocess_mutex atomically with the increment
- mut.unlock();
- }
- //By default, we suppose that no timeout has happened
- bool timed_out = false, unlock_enter_mut= false;
-
- //Loop until a notification indicates that the thread should
- //exit or timeout occurs
- while(1){
- //The thread sleeps/spins until a interprocess_condition commands a notification
- //Notification occurred, we will lock the checking interprocess_mutex so that
- while(detail::atomic_read32(&m_command) == SLEEP){
- detail::thread_yield();
- //Check for timeout
- if(tout_enabled){
- now = microsec_clock::universal_time();
- if(now >= abs_time){
- //If we can lock the interprocess_mutex it means that no notification
- //is being executed in this interprocess_condition variable
- timed_out = m_enter_mut.try_lock();
- //If locking fails, indicates that another thread is executing
- //notification, so we play the notification game
- if(!timed_out){
- //There is an ongoing notification, we will try again later
- continue;
- }
- //No notification in execution, since enter interprocess_mutex is locked.
- //We will execute time-out logic, so we will decrement count,
- //release the enter interprocess_mutex and return false.
- break;
- }
- }
- }
- //If a timeout occurred, the interprocess_mutex will not execute checking logic
- if(tout_enabled && timed_out){
- //Decrement wait count
- detail::atomic_dec32(const_cast<boost::uint32_t*>(&m_num_waiters));
- unlock_enter_mut = true;
- break;
- }
- else{
- boost::uint32_t result = detail::atomic_cas32
- (const_cast<boost::uint32_t*>(&m_command), SLEEP, NOTIFY_ONE);
- if(result == SLEEP){
- //Other thread has been notified and since it was a NOTIFY one
- //command, this thread must sleep again
- continue;
- }
- else if(result == NOTIFY_ONE){
- //If it was a NOTIFY_ONE command, only this thread should
- //exit. This thread has atomically marked command as sleep before
- //so no other thread will exit.
- //Decrement wait count.
- unlock_enter_mut = true;
- detail::atomic_dec32(const_cast<boost::uint32_t*>(&m_num_waiters));
- break;
- }
- else{
- //If it is a NOTIFY_ALL command, all threads should return
- //from do_timed_wait function. Decrement wait count.
- unlock_enter_mut = 1 == detail::atomic_dec32(const_cast<boost::uint32_t*>(&m_num_waiters));
- //Check if this is the last thread of notify_all waiters
- //Only the last thread will release the interprocess_mutex
- if(unlock_enter_mut){
- detail::atomic_cas32(const_cast<boost::uint32_t*>(&m_command), SLEEP, NOTIFY_ALL);
- }
- break;
- }
- }
- }
- //Unlock the enter interprocess_mutex if it is a single notification, if this is
- //the last notified thread in a notify_all or a timeout has occurred
- if(unlock_enter_mut){
- m_enter_mut.unlock();
- }
- //Lock external again before returning from the method
- mut.lock();
- return !timed_out;
- }
- } //namespace interprocess
- } // namespace boost