Condition variable waiters are queued in descending priority order, so

there is no need to wake all waiters to assure that the highest priority
thread is run.  As the semaphore code is written, there was no correctness
problem, but the change improves sem_post() performance.

Pointed out by:	deischen

3 files changed, 6 insertions, 27 deletions

diff --git a/lib/libc_r/uthread/uthread_sem.c b/lib/libc_r/uthread/uthread_sem.c
index 9ed6922..851eca2 100644
--- a/lib/libc_r/uthread/uthread_sem.c
+++ b/lib/libc_r/uthread/uthread_sem.c
@@ -226,15 +226,8 @@ _sem_post(sem_t *sem)
 	pthread_mutex_lock(&(*sem)->lock);
 
 	(*sem)->count++;
-	if ((*sem)->nwaiters > 0) {
-		/*
-		 * We must use pthread_cond_broadcast() rather than
-		 * pthread_cond_signal() in order to assure that the highest
-		 * priority thread is run by the scheduler, since
-		 * pthread_cond_signal() signals waiting threads in FIFO order.
-		 */
-		pthread_cond_broadcast(&(*sem)->gtzero);
-	}
+	if ((*sem)->nwaiters > 0)
+		pthread_cond_signal(&(*sem)->gtzero);
 
 	pthread_mutex_unlock(&(*sem)->lock);
 
diff --git a/lib/libkse/thread/thr_sem.c b/lib/libkse/thread/thr_sem.c
index 9ed6922..851eca2 100644
--- a/lib/libkse/thread/thr_sem.c
+++ b/lib/libkse/thread/thr_sem.c
@@ -226,15 +226,8 @@ _sem_post(sem_t *sem)
 	pthread_mutex_lock(&(*sem)->lock);
 
 	(*sem)->count++;
-	if ((*sem)->nwaiters > 0) {
-		/*
-		 * We must use pthread_cond_broadcast() rather than
-		 * pthread_cond_signal() in order to assure that the highest
-		 * priority thread is run by the scheduler, since
-		 * pthread_cond_signal() signals waiting threads in FIFO order.
-		 */
-		pthread_cond_broadcast(&(*sem)->gtzero);
-	}
+	if ((*sem)->nwaiters > 0)
+		pthread_cond_signal(&(*sem)->gtzero);
 
 	pthread_mutex_unlock(&(*sem)->lock);
 
diff --git a/lib/libpthread/thread/thr_sem.c b/lib/libpthread/thread/thr_sem.c
index 9ed6922..851eca2 100644
--- a/lib/libpthread/thread/thr_sem.c
+++ b/lib/libpthread/thread/thr_sem.c
@@ -226,15 +226,8 @@ _sem_post(sem_t *sem)
 	pthread_mutex_lock(&(*sem)->lock);
 
 	(*sem)->count++;
-	if ((*sem)->nwaiters > 0) {
-		/*
-		 * We must use pthread_cond_broadcast() rather than
-		 * pthread_cond_signal() in order to assure that the highest
-		 * priority thread is run by the scheduler, since
-		 * pthread_cond_signal() signals waiting threads in FIFO order.
-		 */
-		pthread_cond_broadcast(&(*sem)->gtzero);
-	}
+	if ((*sem)->nwaiters > 0)
+		pthread_cond_signal(&(*sem)->gtzero);
 
 	pthread_mutex_unlock(&(*sem)->lock);