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-rw-r--r--src/thread/sem_trywait.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index beb7aa5d..dd8f57e3 100644
--- a/src/thread/sem_trywait.c
+++ b/src/thread/sem_trywait.c
@@ -3,9 +3,8 @@
int sem_trywait(sem_t *sem)
{
- if (a_fetch_add(sem->__val, -1) > 0) return 0;
- if (!a_fetch_add(sem->__val, 1) && sem->__val[1])
- __wake(sem->__val, 1, 0);
+ int val = sem->__val[0];
+ if (val>0 && a_cas(sem->__val, val, val-1)==val) return 0;
errno = EAGAIN;
return -1;
}