add missing memory barrier to pthread_join
authorBobby Bingham <koorogi@koorogi.info>
Sun, 4 Oct 2015 19:55:29 +0000 (14:55 -0500)
committerRich Felker <dalias@aerifal.cx>
Fri, 16 Oct 2015 02:58:59 +0000 (22:58 -0400)
POSIX requires pthread_join to synchronize memory on success.  The
futex wait inside __timedwait_cp cannot handle this because it's not
called in all cases.  Also, in the case of a spurious wake, tid can
become zero between the wake and when the joining thread checks it.

src/thread/pthread_join.c

index 966b4ab0d11eabf4ab208e44e7ca290a10578c51..694d377ad486b834bf3c8453ed092ab684fd1fc9 100644 (file)
@@ -13,6 +13,7 @@ int __pthread_join(pthread_t t, void **res)
        if (cs == PTHREAD_CANCEL_ENABLE) __pthread_setcancelstate(cs, 0);
        while ((tmp = t->tid)) __timedwait_cp(&t->tid, tmp, 0, 0, 0);
        __pthread_setcancelstate(cs, 0);
+       a_barrier();
        if (res) *res = t->result;
        if (t->map_base) __munmap(t->map_base, t->map_size);
        return 0;