Merge pull request git-for-windows#1214 from rongjiecomputer/master

Implement pthread_cond_t with Win32 CONDITION_VARIABLE

Author: dscho

compat/win32/pthread.c

@@ -56,141 +56,3 @@ pthread_t pthread_self(void)
 	t.tid = GetCurrentThreadId();
 	return t;
 }
-
-int pthread_cond_init(pthread_cond_t *cond, const void *unused)
-{
-	cond->waiters = 0;
-	cond->was_broadcast = 0;
-	InitializeCriticalSection(&cond->waiters_lock);
-
-	cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
-	if (!cond->sema)
-		die("CreateSemaphore() failed");
-
-	cond->continue_broadcast = CreateEvent(NULL,	/* security */
-				FALSE,			/* auto-reset */
-				FALSE,			/* not signaled */
-				NULL);			/* name */
-	if (!cond->continue_broadcast)
-		die("CreateEvent() failed");
-
-	return 0;
-}
-
-int pthread_cond_destroy(pthread_cond_t *cond)
-{
-	CloseHandle(cond->sema);
-	CloseHandle(cond->continue_broadcast);
-	DeleteCriticalSection(&cond->waiters_lock);
-	return 0;
-}
-
-int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex)
-{
-	int last_waiter;
-
-	EnterCriticalSection(&cond->waiters_lock);
-	cond->waiters++;
-	LeaveCriticalSection(&cond->waiters_lock);
-
-	/*
-	 * Unlock external mutex and wait for signal.
-	 * NOTE: we've held mutex locked long enough to increment
-	 * waiters count above, so there's no problem with
-	 * leaving mutex unlocked before we wait on semaphore.
-	 */
-	LeaveCriticalSection(mutex);
-
-	/* let's wait - ignore return value */
-	WaitForSingleObject(cond->sema, INFINITE);
-
-	/*
-	 * Decrease waiters count. If we are the last waiter, then we must
-	 * notify the broadcasting thread that it can continue.
-	 * But if we continued due to cond_signal, we do not have to do that
-	 * because the signaling thread knows that only one waiter continued.
-	 */
-	EnterCriticalSection(&cond->waiters_lock);
-	cond->waiters--;
-	last_waiter = cond->was_broadcast && cond->waiters == 0;
-	LeaveCriticalSection(&cond->waiters_lock);
-
-	if (last_waiter) {
-		/*
-		 * cond_broadcast was issued while mutex was held. This means
-		 * that all other waiters have continued, but are contending
-		 * for the mutex at the end of this function because the
-		 * broadcasting thread did not leave cond_broadcast, yet.
-		 * (This is so that it can be sure that each waiter has
-		 * consumed exactly one slice of the semaphor.)
-		 * The last waiter must tell the broadcasting thread that it
-		 * can go on.
-		 */
-		SetEvent(cond->continue_broadcast);
-		/*
-		 * Now we go on to contend with all other waiters for
-		 * the mutex. Auf in den Kampf!
-		 */
-	}
-	/* lock external mutex again */
-	EnterCriticalSection(mutex);
-
-	return 0;
-}
-
-/*
- * IMPORTANT: This implementation requires that pthread_cond_signal
- * is called while the mutex is held that is used in the corresponding
- * pthread_cond_wait calls!
- */
-int pthread_cond_signal(pthread_cond_t *cond)
-{
-	int have_waiters;
-
-	EnterCriticalSection(&cond->waiters_lock);
-	have_waiters = cond->waiters > 0;
-	LeaveCriticalSection(&cond->waiters_lock);
-
-	/*
-	 * Signal only when there are waiters
-	 */
-	if (have_waiters)
-		return ReleaseSemaphore(cond->sema, 1, NULL) ?
-			0 : err_win_to_posix(GetLastError());
-	else
-		return 0;
-}
-
-/*
- * DOUBLY IMPORTANT: This implementation requires that pthread_cond_broadcast
- * is called while the mutex is held that is used in the corresponding
- * pthread_cond_wait calls!
- */
-int pthread_cond_broadcast(pthread_cond_t *cond)
-{
-	EnterCriticalSection(&cond->waiters_lock);
-
-	if ((cond->was_broadcast = cond->waiters > 0)) {
-		/* wake up all waiters */
-		ReleaseSemaphore(cond->sema, cond->waiters, NULL);
-		LeaveCriticalSection(&cond->waiters_lock);
-		/*
-		 * At this point all waiters continue. Each one takes its
-		 * slice of the semaphor. Now it's our turn to wait: Since
-		 * the external mutex is held, no thread can leave cond_wait,
-		 * yet. For this reason, we can be sure that no thread gets
-		 * a chance to eat *more* than one slice. OTOH, it means
-		 * that the last waiter must send us a wake-up.
-		 */
-		WaitForSingleObject(cond->continue_broadcast, INFINITE);
-		/*
-		 * Since the external mutex is held, no thread can enter
-		 * cond_wait, and, hence, it is safe to reset this flag
-		 * without cond->waiters_lock held.
-		 */
-		cond->was_broadcast = 0;
-	} else {
-		LeaveCriticalSection(&cond->waiters_lock);
-	}
-	return 0;
-}

compat/win32/pthread.h

@@ -32,27 +32,24 @@ typedef int pthread_mutexattr_t;
 #define pthread_mutexattr_settype(a, t) 0
 #define PTHREAD_MUTEX_RECURSIVE 0
 
-/*
- * Implement simple condition variable for Windows threads, based on ACE
- * implementation.
- *
- * See original implementation: http://bit.ly/1vkDjo
- * ACE homepage: http://www.cse.wustl.edu/~schmidt/ACE.html
- * See also: http://www.cse.wustl.edu/~schmidt/win32-cv-1.html
- */
-typedef struct {
-	LONG waiters;
-	int was_broadcast;
-	CRITICAL_SECTION waiters_lock;
-	HANDLE sema;
-	HANDLE continue_broadcast;
-} pthread_cond_t;
-
-extern int pthread_cond_init(pthread_cond_t *cond, const void *unused);
-extern int pthread_cond_destroy(pthread_cond_t *cond);
-extern int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex);
-extern int pthread_cond_signal(pthread_cond_t *cond);
-extern int pthread_cond_broadcast(pthread_cond_t *cond);
+#define pthread_cond_t CONDITION_VARIABLE
+
+WINBASEAPI VOID WINAPI
+InitializeConditionVariable(PCONDITION_VARIABLE ConditionVariable);
+WINBASEAPI VOID WINAPI
+WakeConditionVariable(PCONDITION_VARIABLE ConditionVariable);
+WINBASEAPI VOID WINAPI
+WakeAllConditionVariable(PCONDITION_VARIABLE ConditionVariable);
+WINBASEAPI BOOL WINAPI
+SleepConditionVariableCS(PCONDITION_VARIABLE ConditionVariable,
+                         PCRITICAL_SECTION CriticalSection,
+                         DWORD dwMilliseconds);
+
+#define pthread_cond_init(a,b) InitializeConditionVariable((a))
+#define pthread_cond_destroy(a) do {} while (0)
+#define pthread_cond_wait(a,b) return_0(SleepConditionVariableCS((a), (b), INFINITE))
+#define pthread_cond_signal WakeConditionVariable
+#define pthread_cond_broadcast WakeAllConditionVariable
 
 /*
  * Simple thread creation implementation using pthread API