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From 77950da440c2b12c153b77ab8b4d1d00c88ca3a9 Mon Sep 17 00:00:00 2001
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From: "H.J. Lu" <hjl.tools@gmail.com>
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Date: Fri, 12 Nov 2021 11:47:42 -0800
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Subject: [PATCH] Move assignment out of the CAS condition
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Update
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commit 49302b8fdf9103b6fc0a398678668a22fa19574c
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Author: H.J. Lu <hjl.tools@gmail.com>
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Date: Thu Nov 11 06:54:01 2021 -0800
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Avoid extra load with CAS in __pthread_mutex_clocklock_common [BZ #28537]
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Replace boolean CAS with value CAS to avoid the extra load.
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and
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commit 0b82747dc48d5bf0871bdc6da8cb6eec1256355f
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Author: H.J. Lu <hjl.tools@gmail.com>
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Date: Thu Nov 11 06:31:51 2021 -0800
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Avoid extra load with CAS in __pthread_mutex_lock_full [BZ #28537]
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Replace boolean CAS with value CAS to avoid the extra load.
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by moving assignment out of the CAS condition.
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(cherry picked from commit 120ac6d238825452e8024e2f627da33b2508dfd3)
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---
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nptl/pthread_mutex_lock.c | 7 +++----
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nptl/pthread_mutex_timedlock.c | 7 +++----
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2 files changed, 6 insertions(+), 8 deletions(-)
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diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
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index eb4d8baa..a633d95e 100644
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--- a/nptl/pthread_mutex_lock.c
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+++ b/nptl/pthread_mutex_lock.c
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@@ -299,10 +299,9 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
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meantime. */
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if ((oldval & FUTEX_WAITERS) == 0)
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{
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- int val;
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- if ((val = atomic_compare_and_exchange_val_acq
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- (&mutex->__data.__lock, oldval | FUTEX_WAITERS,
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- oldval)) != oldval)
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+ int val = atomic_compare_and_exchange_val_acq
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+ (&mutex->__data.__lock, oldval | FUTEX_WAITERS, oldval);
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+ if (val != oldval)
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{
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oldval = val;
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continue;
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diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
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index c4627ef6..a76c30b7 100644
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--- a/nptl/pthread_mutex_timedlock.c
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+++ b/nptl/pthread_mutex_timedlock.c
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@@ -269,10 +269,9 @@ __pthread_mutex_timedlock (pthread_mutex_t *mutex,
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meantime. */
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if ((oldval & FUTEX_WAITERS) == 0)
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{
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- int val;
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- if ((val = atomic_compare_and_exchange_val_acq
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- (&mutex->__data.__lock, oldval | FUTEX_WAITERS,
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- oldval)) != oldval)
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+ int val = atomic_compare_and_exchange_val_acq
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+ (&mutex->__data.__lock, oldval | FUTEX_WAITERS, oldval);
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+ if (val != oldval)
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{
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oldval = val;
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continue;
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--
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GitLab
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