X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fthread%2Fsem_trywait.c;h=55d90075e274a5e0a82359ffc96e6b45a279e286;hb=9372655e884b3829c6639fc1a6047b2569f3c3ec;hp=c5370c70a7f397751d7a124df03a5c1afe78eec9;hpb=cfe581b6bc795e3f00ac30791314ec0f9be4b4ad;p=musl

diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index c5370c70..55d90075 100644
--- a/src/thread/sem_trywait.c
+++ b/src/thread/sem_trywait.c
@@ -3,10 +3,11 @@
 
 int sem_trywait(sem_t *sem)
 {
-	int val = a_fetch_add(sem->__val, -1);
-	if (val > 0) return 0;
-	if (!a_fetch_add(sem->__val, 1))
-		__wake(sem->__val, 1, 0);
+	int val = sem->__val[0];
+	if (val>0) {
+		int new = val-1-(val==1 && sem->__val[1]);
+		if (a_cas(sem->__val, val, new)==val) return 0;
+	}
 	errno = EAGAIN;
 	return -1;
 }