void Signal(bool all = FALSE);
private:
- // the number of Signal() calls queued
- //
- // changed by Signal(), accessed by Wait()
- //
- // protected by m_mutexSignalCount
- size_t m_nSignalsMissed;
-
- // protects access to m_nSignalsMissed
- pthread_mutex_t m_mutexSignalCount;
-
- // serializes Broadcast() and/or Signal() calls
- //
- // TODO: I'm not sure if this is really needed but it shouldn't harm
- // neither (except for efficiency condierations). However MSW doesn't
- // do this so maybe we shouldn't do it here neither? (VZ)
- pthread_mutex_t m_mutexSignal;
+ // the number of Signal() calls we "missed", i.e. which were done while
+ // there were no threads to wait for them
+ size_t m_nQueuedSignals;
- // a condition variable must be always used with a mutex and so we maintain
- // a list of mutexes - one for each thread that calls Wait().
- //
- // access to this list must be protected by m_mutexListContents
- wxMutexList m_mutexes;
+ // counts all pending waiters
+ size_t m_nWaiters;
// the condition itself
pthread_cond_t m_condition;
- // protects all accesses to m_mutexes list
- pthread_mutex_t m_mutexListContents;
+ // the mutex used with the conditon: it also protects the counters above
+ pthread_mutex_t m_mutex;
};
wxConditionInternal::wxConditionInternal()
{
- m_nSignalsMissed = 0;
+ m_nQueuedSignals =
+ m_nWaiters = 0;
if ( pthread_cond_init(&m_condition, (pthread_condattr_t *)NULL) != 0 )
{
wxFAIL_MSG( _T("pthread_cond_init() failed") );
}
- if ( pthread_mutex_init(&m_mutexSignalCount, NULL) != 0 ||
- pthread_mutex_init(&m_mutexListContents, NULL) != 0 ||
- pthread_mutex_init(&m_mutexSignal, NULL) != 0 )
+ if ( pthread_mutex_init(&m_mutex, NULL) != 0 )
{
// neither this
wxFAIL_MSG( _T("wxCondition: pthread_mutex_init() failed") );
"threads are probably still waiting on it?)"));
}
- // the list of waiters mutexes must be empty by now
- wxASSERT_MSG( !m_mutexes.GetFirst(),
- _T("deleting condition someone is still waiting on?") );
-
- if ( pthread_mutex_destroy( &m_mutexSignalCount ) != 0 ||
- pthread_mutex_destroy( &m_mutexListContents ) != 0 ||
- pthread_mutex_destroy( &m_mutexSignal ) != 0 )
+ if ( pthread_mutex_destroy( &m_mutex ) != 0 )
{
wxLogDebug(_T("Failed to destroy mutex (it is probably locked)"));
}
bool wxConditionInternal::Wait(const timespec* ts)
{
+ MutexLock lock(m_mutex);
+
+ if ( m_nQueuedSignals )
{
+ m_nQueuedSignals--;
+
wxLogTrace(TRACE_THREADS,
- _T("wxCondition(%08x)::Wait: about to lock missed signal counter"),
+ _T("wxCondition(%08x)::Wait(): Has been signaled before"),
this);
- MutexLock lock(m_mutexSignalCount);
-
- if ( m_nSignalsMissed )
- {
- // the condition was signaled before we started to wait, just
- // decrease the number of queued signals and return
- m_nSignalsMissed--;
-
- wxLogTrace(TRACE_THREADS,
- _T("wxCondition(%08x)::Wait: not waiting at all, count = %u"),
- this, m_nSignalsMissed);
-
- return TRUE;
- }
+ return TRUE;
}
- // we need to really wait, create a new mutex for this
- pthread_mutex_t *mutex = new pthread_mutex_t;
- if ( pthread_mutex_init(mutex, (pthread_mutexattr_t *)NULL) != 0 )
- {
- // not supposed to happen
- wxFAIL_MSG( _T("pthread_mutex_init() failed when starting waiting") );
- }
-
- // lock the mutex before starting to wait on it
- pthread_mutex_lock(mutex);
-
- // lock the list before modifying it
- wxMutexList::Node *mutexNode;
- {
- MutexLock lockList(m_mutexListContents);
-
- mutexNode = m_mutexes.Append(mutex);
- }
+ // there are no queued signals, so start really waiting
+ m_nWaiters++;
// calling wait function below unlocks the mutex and Signal() or
// Broadcast() will be able to continue to run now if they were
// blocking for it in the loop locking all mutexes)
wxLogTrace(TRACE_THREADS,
_T("wxCondition(%08x)::Wait(): starting to wait"), this);
- int err = ts ? pthread_cond_timedwait(&m_condition, mutex, ts)
- : pthread_cond_wait(&m_condition, mutex);
+
+ int err = ts ? pthread_cond_timedwait(&m_condition, &m_mutex, ts)
+ : pthread_cond_wait(&m_condition, &m_mutex);
switch ( err )
{
case 0:
case ETIMEDOUT:
case EINTR:
+ // The condition has not been signaled, so we have to
+ // decrement the counter manually
+ --m_nWaiters;
+
// wait interrupted or timeout elapsed
wxLogTrace(TRACE_THREADS,
_T("wxCondition(%08x)::Wait(): timeout/intr"), this);
}
- // delete the mutex we had used for waiting
- {
- MutexLock lock(m_mutexListContents);
-
- pthread_mutex_t *m = mutexNode->GetData();
- pthread_mutex_unlock(m);
- pthread_mutex_destroy(m);
- delete m;
-
- m_mutexes.DeleteNode(mutexNode);
- }
-
return err == 0;
}
void wxConditionInternal::Signal(bool all)
{
// make sure that only one Signal() or Broadcast() is in progress
- MutexLock lock(m_mutexSignal);
-
- // this mutex has to be locked as well, so that during the entire Signal()
- // call, no new Wait() is going to wreak havoc (it will block in the very
- // beginning on this mutex instead)
- MutexLock lockSignalCount(m_mutexSignalCount);
-
- wxLogTrace(TRACE_THREADS,
- _T("wxCondition(%08x)::Signal(): got signal count mutex"),
- this);
+ MutexLock lock(m_mutex);
+ // Are there any waiters?
+ if ( m_nWaiters == 0 )
{
- MutexLock lockList(m_mutexListContents);
-
- if ( !m_mutexes.GetFirst() )
- {
- // nobody is waiting for us, just remember that the condition was
- // signaled and don't do anything else for now
- m_nSignalsMissed++;
-
- wxLogTrace(TRACE_THREADS,
- _T("wxCondition(%08x)::Signal(): no waiters, count = %u"),
- this, m_nSignalsMissed);
-
- return;
- }
- }
-
- wxLogTrace(TRACE_THREADS,
- _T("wxCondition(%08x)::Signal(): acquiring all mutexes"), this);
+ // No, there are not, so don't signal but keep in mind for the next
+ // Wait()
+ m_nQueuedSignals++;
- // All mutexes on the list have to be locked. This means that execution of
- // Signal() goes on as soon as all pending Wait() calls have called
- // pthread_cond_wait() (where the mutex gets unlocked internally)
- wxMutexList::Node *node;
- for ( node = m_mutexes.GetFirst(); node; node = node->GetNext() )
- {
- pthread_mutex_lock(node->GetData());
+ return;
}
// now we can finally signal it
int err = all ? pthread_cond_broadcast(&m_condition)
: pthread_cond_signal(&m_condition);
- if ( err )
+
+ if ( all )
{
- // shouldn't ever happen
- wxFAIL_MSG(_T("pthread_cond_{broadcast|signal}() failed"));
+ m_nWaiters = 0;
}
-
- // unlock all mutexes so that the threads blocking in their Wait()s could
- // continue running
- for ( node = m_mutexes.GetFirst(); node; node = node->GetNext() )
+ else
{
- pthread_mutex_unlock(node->GetData());
+ --m_nWaiters;
}
- wxLogTrace(TRACE_THREADS,
- _T("wxCondition(%08x)::Signal(): exiting"), this);
+ if ( err )
+ {
+ // shouldn't ever happen
+ wxFAIL_MSG(_T("pthread_cond_{broadcast|signal}() failed"));
+ }
}
// ----------------------------------------------------------------------------
projects / wxWidgets.git / commitdiff
