synchronize cond var destruction with exiting waits

[oweals/musl.git] / src / thread / sem_trywait.c

diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index c5370c70a7f397751d7a124df03a5c1afe78eec9..55d90075e274a5e0a82359ffc96e6b45a279e286 100644 (file)
--- 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;
 }