glibc/glibc-rh1622675.patch

28 lines
1.2 KiB
Diff

commit aa8a3e4cdef20c50cb20f008864fff05cbfbdf29
Author: Martin Kuchta <martin.kuchta@netapp.com>
Date: Mon Aug 27 18:54:46 2018 +0200
pthread_cond_broadcast: Fix waiters-after-spinning case [BZ #23538]
(cherry picked from commit 99ea93ca31795469d2a1f1570f17a5c39c2eb7e2)
diff --git a/nptl/pthread_cond_common.c b/nptl/pthread_cond_common.c
index 8e425eb01eceabec..479e54febb417675 100644
--- a/nptl/pthread_cond_common.c
+++ b/nptl/pthread_cond_common.c
@@ -405,8 +405,12 @@ __condvar_quiesce_and_switch_g1 (pthread_cond_t *cond, uint64_t wseq,
{
/* There is still a waiter after spinning. Set the wake-request
flag and block. Relaxed MO is fine because this is just about
- this futex word. */
- r = atomic_fetch_or_relaxed (cond->__data.__g_refs + g1, 1);
+ this futex word.
+
+ Update r to include the set wake-request flag so that the upcoming
+ futex_wait only blocks if the flag is still set (otherwise, we'd
+ violate the basic client-side futex protocol). */
+ r = atomic_fetch_or_relaxed (cond->__data.__g_refs + g1, 1) | 1;
if ((r >> 1) > 0)
futex_wait_simple (cond->__data.__g_refs + g1, r, private);