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glibc/SOURCES/glibc-RHEL-15696-64.patch

40 lines
1.2 KiB

From 0b82747dc48d5bf0871bdc6da8cb6eec1256355f Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 11 Nov 2021 06:31:51 -0800
Subject: [PATCH] Avoid extra load with CAS in __pthread_mutex_lock_full [BZ
#28537]
Content-type: text/plain; charset=UTF-8
Replace boolean CAS with value CAS to avoid the extra load.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
---
nptl/pthread_mutex_lock.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 29cc143e..60ada70d 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -292,12 +292,12 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
meantime. */
if ((oldval & FUTEX_WAITERS) == 0)
{
- if (atomic_compare_and_exchange_bool_acq (&mutex->__data.__lock,
- oldval | FUTEX_WAITERS,
- oldval)
- != 0)
+ int val;
+ if ((val = atomic_compare_and_exchange_val_acq
+ (&mutex->__data.__lock, oldval | FUTEX_WAITERS,
+ oldval)) != oldval)
{
- oldval = mutex->__data.__lock;
+ oldval = val;
continue;
}
oldval |= FUTEX_WAITERS;
--
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