X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=blobdiff_plain;f=src%2Fthread%2Fsem_trywait.c;h=04edf46b524de72a575b1db7687f56d93fc1e291;hp=d0e928ef67d2048f4bbf1f1214a30407d8dbe7c8;hb=8c0a3d9e5c169fc9d0f246ab59362b658b029ad7;hpb=6fc5fdbdc70dd17ea8e681a361fb4dae541ee953;ds=sidebyside

diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index d0e928ef..04edf46b 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;
+	while ((val=sem->__val[0]) > 0) {
+		int new = val-1-(val==1 && sem->__val[1]);
+		if (a_cas(sem->__val, val, new)==val) return 0;
+	}
 	errno = EAGAIN;
 	return -1;
 }