1 files changed, 8 insertions, 4 deletions
diff --git a/src/thread/sem_post.c b/src/thread/sem_post.c
index 31e3293d..5c2517f2 100644
--- a/src/thread/sem_post.c
+++ b/src/thread/sem_post.c
@@ -1,17 +1,21 @@
 #include <semaphore.h>
+#include <limits.h>
 #include "pthread_impl.h"
 
 int sem_post(sem_t *sem)
 {
-	int val, waiters, priv = sem->__val[2];
+	int val, new, waiters, priv = sem->__val[2];
 	do {
 		val = sem->__val[0];
 		waiters = sem->__val[1];
-		if (val == SEM_VALUE_MAX) {
+		if ((val & SEM_VALUE_MAX) == SEM_VALUE_MAX) {
 			errno = EOVERFLOW;
 			return -1;
 		}
-	} while (a_cas(sem->__val, val, val+1+(val<0)) != val);
-	if (val<0 || waiters) __wake(sem->__val, 1, priv);
+		new = val + 1;
+		if (waiters <= 1)
+			new &= ~0x80000000;
+	} while (a_cas(sem->__val, val, new) != val);
+	if (val<0) __wake(sem->__val, waiters>1 ? 1 : -1, priv);
 	return 0;
 }