X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=blobdiff_plain;f=compat%2Fwin32%2Fpthread.c;h=010e875ec4dd8d7154a0911661570165ac1ae874;hb=78db709ae59da26de76264b79df3a7dc4d87e65c;hp=631c0a46ea3ddc4daaa773128b4a3e7a001653de;hpb=844ad3d9a0418b4a3a6a944a50d65403121a0eb6;p=git.git

diff --git a/compat/win32/pthread.c b/compat/win32/pthread.c
index 631c0a46e..010e875ec 100644
--- a/compat/win32/pthread.c
+++ b/compat/win32/pthread.c
@@ -1,7 +1,7 @@
 /*
  * Copyright (C) 2009 Andrzej K. Haczewski <ahaczewski@gmail.com>
  *
- * DISCLAMER: The implementation is Git-specific, it is subset of original
+ * DISCLAIMER: The implementation is Git-specific, it is subset of original
  * Pthreads API, without lots of other features that Git doesn't use.
  * Git also makes sure that the passed arguments are valid, so there's
  * no need for double-checking.
@@ -16,6 +16,7 @@
 static unsigned __stdcall win32_start_routine(void *arg)
 {
 	pthread_t *thread = arg;
+	thread->tid = GetCurrentThreadId();
 	thread->arg = thread->start_routine(thread->arg);
 	return 0;
 }
@@ -49,27 +50,48 @@ int win32_pthread_join(pthread_t *thread, void **value_ptr)
 	}
 }
 
+pthread_t pthread_self(void)
+{
+	pthread_t t = { 0 };
+	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);
-	cond->sema = NULL;
-
+	CloseHandle(cond->continue_broadcast);
+	DeleteCriticalSection(&cond->waiters_lock);
 	return 0;
 }
 
 int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex)
 {
-	InterlockedIncrement(&cond->waiters);
+	int last_waiter;
+
+	EnterCriticalSection(&cond->waiters_lock);
+	cond->waiters++;
+	LeaveCriticalSection(&cond->waiters_lock);
 
 	/*
 	 * Unlock external mutex and wait for signal.
@@ -82,22 +104,52 @@ int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex)
 	/* let's wait - ignore return value */
 	WaitForSingleObject(cond->sema, INFINITE);
 
-	/* we're done waiting, so make sure we decrease waiters count */
-	InterlockedDecrement(&cond->waiters);
-
+	/*
+	 * 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)
 {
-	/*
-	 * Access to waiters count is atomic; see "Interlocked Variable Access"
-	 * http://msdn.microsoft.com/en-us/library/ms684122(VS.85).aspx
-	 */
-	int have_waiters = cond->waiters > 0;
+	int have_waiters;
+
+	EnterCriticalSection(&cond->waiters_lock);
+	have_waiters = cond->waiters > 0;
+	LeaveCriticalSection(&cond->waiters_lock);
 
 	/*
 	 * Signal only when there are waiters
@@ -108,3 +160,37 @@ int pthread_cond_signal(pthread_cond_t *cond)
 	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;
+}