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/*========================================================================= |
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Program: Insight Segmentation & Registration Toolkit |
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Module: $RCSfile: itkConditionVariable.cxx.html,v $ |
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Language: C++ |
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Date: $Date: 2006/01/17 19:15:34 $ |
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Version: $Revision: 1.4 $ |
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Copyright (c) Insight Software Consortium. All rights reserved. |
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See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details. |
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This software is distributed WITHOUT ANY WARRANTY; without even |
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR |
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PURPOSE. See the above copyright notices for more information. |
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=========================================================================*/ |
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DEF |
#ifndef _itkConditionVariable_cxx_ |
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DEF |
#define _itkConditionVariable_cxx_ |
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#include "itkConditionVariable.h" |
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namespace itk { |
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ConditionVariable::ConditionVariable() |
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{ |
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#ifdef ITK_USE_PTHREADS |
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pthread_mutex_init(&m_Mutex, NULL); |
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pthread_cond_init(&m_ConditionVariable, NULL); |
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#else |
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#ifdef WIN32 |
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m_NumberOfWaiters = 0; |
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m_WasBroadcast = 0; |
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m_Semaphore = CreateSemaphore(NULL, // no security |
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0, // initial value |
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0x7fffffff, // max count |
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NULL); // unnamed |
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InitializeCriticalSection( &m_NumberOfWaitersLock ); |
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m_WaitersAreDone = CreateEvent( NULL, // no security |
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FALSE, // auto-reset |
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FALSE, // non-signaled initially |
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NULL ); // unnamed |
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#endif |
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#endif |
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} |
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ConditionVariable::~ConditionVariable() |
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{ |
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#ifdef ITK_USE_PTHREADS |
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pthread_mutex_destroy(&m_Mutex); |
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pthread_cond_destroy(&m_ConditionVariable); |
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IND |
#else |
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#ifdef WIN32 |
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CloseHandle( m_Semaphore ); |
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CloseHandle( m_WaitersAreDone ); |
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DeleteCriticalSection( &m_NumberOfWaitersLock ); |
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#endif |
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#endif |
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} |
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void ConditionVariable::Signal() |
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{ |
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#ifdef ITK_USE_PTHREADS |
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pthread_cond_signal(&m_ConditionVariable); |
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#else |
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#ifdef WIN32 |
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EnterCriticalSection( &m_NumberOfWaitersLock ); |
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int haveWaiters = m_NumberOfWaiters > 0; |
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LeaveCriticalSection( &m_NumberOfWaitersLock ); |
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// if there were not any waiters, then this is a no-op |
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if (haveWaiters) |
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{ |
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ReleaseSemaphore(m_Semaphore, 1, 0); |
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} |
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#endif |
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#endif |
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} |
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void ConditionVariable::Broadcast() |
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{ |
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#ifdef ITK_USE_PTHREADS |
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pthread_cond_broadcast(&m_ConditionVariable); |
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#else |
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#ifdef WIN32 |
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// This is needed to ensure that m_NumberOfWaiters and m_WasBroadcast are |
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// consistent |
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EnterCriticalSection( &m_NumberOfWaitersLock ); |
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int haveWaiters = 0; |
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if (m_NumberOfWaiters > 0) |
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{ |
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// We are broadcasting, even if there is just one waiter... |
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// Record that we are broadcasting, which helps optimize Wait() |
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// for the non-broadcast case |
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m_WasBroadcast = 1; |
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haveWaiters = 1; |
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} |
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if (haveWaiters) |
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{ |
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// Wake up all waiters atomically |
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ReleaseSemaphore(m_Semaphore, m_NumberOfWaiters, 0); |
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LeaveCriticalSection( &m_NumberOfWaitersLock ); |
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// Wait for all the awakened threads to acquire the counting |
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// semaphore |
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WaitForSingleObject( m_WaitersAreDone, INFINITE ); |
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// This assignment is ok, even without the m_NumberOfWaitersLock held |
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// because no other waiter threads can wake up to access it. |
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m_WasBroadcast = 0; |
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} |
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else |
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{ |
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LeaveCriticalSection( &m_NumberOfWaitersLock ); |
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} |
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#endif |
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#endif |
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} |
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void ConditionVariable::Wait(SimpleMutexLock *mutex) |
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{ |
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#ifdef ITK_USE_PTHREADS |
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pthread_cond_wait(&m_ConditionVariable, &mutex->GetMutexLock() ); |
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#else |
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#ifdef WIN32 |
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// Avoid race conditions |
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EnterCriticalSection( &m_NumberOfWaitersLock ); |
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m_NumberOfWaiters++; |
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LeaveCriticalSection( &m_NumberOfWaitersLock ); |
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// This call atomically releases the mutex and waits on the |
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// semaphore until signaled |
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SignalObjectAndWait( mutex->GetMutexLock(), m_Semaphore, INFINITE, FALSE ); |
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// Reacquire lock to avoid race conditions |
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EnterCriticalSection( &m_NumberOfWaitersLock ); |
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// We're no longer waiting.... |
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m_NumberOfWaiters--; |
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// Check to see if we're the last waiter after the broadcast |
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int lastWaiter = m_WasBroadcast && m_NumberOfWaiters == 0; |
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LeaveCriticalSection( &m_NumberOfWaitersLock ); |
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// If we're the last waiter thread during this particular broadcast |
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// then let the other threads proceed |
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if (lastWaiter) |
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{ |
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// This call atomically signals the m_WaitersAreDone event and waits |
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// until it can acquire the external mutex. This is required to |
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// ensure fairness |
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SignalObjectAndWait( m_WaitersAreDone, mutex->GetMutexLock(), INFINITE, FALSE); |
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} |
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else |
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{ |
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// Always regain the external mutex since that's the guarentee we |
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// give to our callers |
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WaitForSingleObject( mutex->GetMutexLock(), INFINITE ); |
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} |
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#endif |
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#endif |
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} |
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}//end of namespace itk |
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#endif |
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