overhaul aio implementation for correctness

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

diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index dd8f57e36a0bd54a60a5b4c21516b9a1b6a8bba5..04edf46b524de72a575b1db7687f56d93fc1e291 100644 (file)
--- a/src/thread/sem_trywait.c
+++ b/src/thread/sem_trywait.c
@@ -3,8 +3,11 @@
 
 int sem_trywait(sem_t *sem)
 {
-       int val = sem->__val[0];
-       if (val>0 && a_cas(sem->__val, val, val-1)==val) return 0;
+       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;
 }