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GNU C Library master sources branch master updated. glibc-2.28.9000-96-g99ea93c
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- To: glibc-cvs at sourceware dot org
- Date: 27 Aug 2018 15:28:31 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.28.9000-96-g99ea93c
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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=99ea93ca31795469d2a1f1570f17a5c39c2eb7e2
commit 99ea93ca31795469d2a1f1570f17a5c39c2eb7e2
Author: Martin Kuchta <martin.kuchta@netapp.com>
Date: Mon Aug 27 17:03:35 2018 +0200
pthread_cond_broadcast: Fix waiters-after-spinning case [BZ #23538]
diff --git a/ChangeLog b/ChangeLog
index f97c551..9fc0060 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2018-08-27 Martin Kuchta <martin.kuchta@netapp.com>
+ Torvald Riegel <triegel@redhat.com>
+
+ [BZ #23538]
+ * nptl/pthread_cond_common.c (__condvar_quiesce_and_switch_g1):
+ Update r to include the set wake-request flag if waiters are
+ remaining after spinning.
+
2018-08-27 Joseph Myers <joseph@codesourcery.com>
* sysdeps/gnu/netinet/udp.h (UDP_SEGMENT): New macro.
diff --git a/nptl/pthread_cond_common.c b/nptl/pthread_cond_common.c
index 8e425eb..479e54f 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);
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 8 ++++++++
nptl/pthread_cond_common.c | 8 ++++++--
2 files changed, 14 insertions(+), 2 deletions(-)
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