work around a nasty bug in linux readv syscall

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

diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index c5370c70a7f397751d7a124df03a5c1afe78eec9..beb7aa5d3d359b793e11bf106ee21dda92feef73 100644 (file)
--- a/src/thread/sem_trywait.c
+++ b/src/thread/sem_trywait.c
@@ -3,9 +3,8 @@
 
 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))
+       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);
        errno = EAGAIN;
        return -1;