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From: Sunil Pandey <skpgkp2@sourceware.org>
To: glibc-cvs@sourceware.org
Subject: [glibc/users/skpgkp2/2.33/master] Move assignment out of the CAS condition
Date: Thu, 29 Sep 2022 18:41:39 +0000 (GMT)	[thread overview]
Message-ID: <20220929184139.68E6F385C412@sourceware.org> (raw)

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=60b8295333a076ff853c1093c502c7bf5197ab2e

commit 60b8295333a076ff853c1093c502c7bf5197ab2e
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Fri Nov 12 11:47:42 2021 -0800

    Move assignment out of the CAS condition
    
    Update
    
    commit 49302b8fdf9103b6fc0a398678668a22fa19574c
    Author: H.J. Lu <hjl.tools@gmail.com>
    Date:   Thu Nov 11 06:54:01 2021 -0800
    
        Avoid extra load with CAS in __pthread_mutex_clocklock_common [BZ #28537]
    
        Replace boolean CAS with value CAS to avoid the extra load.
    
    and
    
    commit 0b82747dc48d5bf0871bdc6da8cb6eec1256355f
    Author: H.J. Lu <hjl.tools@gmail.com>
    Date:   Thu Nov 11 06:31:51 2021 -0800
    
        Avoid extra load with CAS in __pthread_mutex_lock_full [BZ #28537]
    
        Replace boolean CAS with value CAS to avoid the extra load.
    
    by moving assignment out of the CAS condition.
    
    (cherry picked from commit 120ac6d238825452e8024e2f627da33b2508dfd3)

Diff:
---
 nptl/pthread_mutex_lock.c      | 7 +++----
 nptl/pthread_mutex_timedlock.c | 7 +++----
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index ac8a472c08..2895926953 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -296,10 +296,9 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
 	     meantime.  */
 	  if ((oldval & FUTEX_WAITERS) == 0)
 	    {
-	      int val;
-	      if ((val = atomic_compare_and_exchange_val_acq
-		   (&mutex->__data.__lock, oldval | FUTEX_WAITERS,
-		    oldval)) != oldval)
+	      int val = atomic_compare_and_exchange_val_acq
+		(&mutex->__data.__lock, oldval | FUTEX_WAITERS, oldval);
+	      if (val != oldval)
 		{
 		  oldval = val;
 		  continue;
diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
index 541ec18938..22174f74c9 100644
--- a/nptl/pthread_mutex_timedlock.c
+++ b/nptl/pthread_mutex_timedlock.c
@@ -247,10 +247,9 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
 	     meantime.  */
 	  if ((oldval & FUTEX_WAITERS) == 0)
 	    {
-	      int val;
-	      if ((val = atomic_compare_and_exchange_val_acq
-		   (&mutex->__data.__lock, oldval | FUTEX_WAITERS,
-		    oldval)) != oldval)
+	      int val = atomic_compare_and_exchange_val_acq
+		(&mutex->__data.__lock, oldval | FUTEX_WAITERS, oldval);
+	      if (val != oldval)
 		{
 		  oldval = val;
 		  continue;

             reply	other threads:[~2022-09-29 18:41 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-29 18:41 Sunil Pandey [this message]
  -- strict thread matches above, loose matches on Subject: below --
2022-09-28 21:45 Sunil Pandey
2022-09-28 19:11 Sunil Pandey

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