X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fthread%2Fsem_trywait.c;h=55d90075e274a5e0a82359ffc96e6b45a279e286;hb=28c5d46d844684feba2ddfc9027ea308d8d3612c;hp=d0e928ef67d2048f4bbf1f1214a30407d8dbe7c8;hpb=6fc5fdbdc70dd17ea8e681a361fb4dae541ee953;p=musl

diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index d0e928ef..55d90075 100644
--- a/src/thread/sem_trywait.c
+++ b/src/thread/sem_trywait.c
@@ -3,9 +3,11 @@
 
 int sem_trywait(sem_t *sem)
 {
-	int val = a_fetch_add(sem->__val, -1);
-	if (val > 0) return 0;
-	a_inc(sem->__val);
+	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;
 }