From: Sunil Pandey <skpgkp2@gmail.com>
To: Andreas Schwab <schwab@linux-m68k.org>,
Libc-stable Mailing List <libc-stable@sourceware.org>
Cc: "H.J. Lu" <hjl.tools@gmail.com>,
Florian Weimer <fweimer@redhat.com>,
GNU C Library <libc-alpha@sourceware.org>,
Arjan van de Ven <arjan@linux.intel.com>,
"Paul A . Clarke" <pc@us.ibm.com>
Subject: Re: [PATCH v6 2/4] Avoid extra load with CAS in __pthread_mutex_lock_full [BZ #28537]
Date: Sun, 11 Sep 2022 13:16:18 -0700 [thread overview]
Message-ID: <CAMAf5_d+Q1e6AWdhzi5d0LaV1et6a6RNLbo+c_mYnt5Gm43-gA@mail.gmail.com> (raw)
In-Reply-To: <87zgq9rywl.fsf@igel.home>
On Fri, Nov 12, 2021 at 10:52 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
>
> On Nov 11 2021, H.J. Lu wrote:
>
> > diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
> > index 72058c719c..762059b230 100644
> > --- a/nptl/pthread_mutex_lock.c
> > +++ b/nptl/pthread_mutex_lock.c
> > @@ -304,12 +304,12 @@ __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)
>
> Please move the assignment out of the condition.
>
> Andreas.
>
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
> "And now for something completely different."
I would like to backport this patch to release branch 2.33 and 2.34
Any comments/suggestions or objections on this.
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.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
next prev parent reply other threads:[~2022-09-11 20:16 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-11 16:24 [PATCH v6 0/4] Optimize CAS " H.J. Lu
2021-11-11 16:24 ` [PATCH v6 1/4] Add LLL_MUTEX_READ_LOCK " H.J. Lu
2021-11-12 17:23 ` Szabolcs Nagy
2021-11-17 2:24 ` Noah Goldstein
2021-11-17 23:54 ` H.J. Lu
2021-11-18 0:03 ` Noah Goldstein
2021-11-18 0:31 ` H.J. Lu
2021-11-18 1:16 ` Arjan van de Ven
2022-09-11 20:19 ` Sunil Pandey
2022-09-29 0:10 ` Noah Goldstein
2021-11-11 16:24 ` [PATCH v6 2/4] Avoid extra load with CAS in __pthread_mutex_lock_full " H.J. Lu
2021-11-12 16:31 ` Szabolcs Nagy
2021-11-12 18:50 ` Andreas Schwab
2022-09-11 20:16 ` Sunil Pandey [this message]
2022-09-29 0:10 ` Noah Goldstein
2021-11-11 16:24 ` [PATCH v6 3/4] Reduce CAS in malloc spinlocks H.J. Lu
2023-02-23 5:48 ` DJ Delorie
2021-11-11 16:24 ` [PATCH v6 4/4] Avoid extra load with CAS in __pthread_mutex_clocklock_common [BZ #28537] H.J. Lu
2021-11-12 16:32 ` Szabolcs Nagy
2021-11-12 18:51 ` Andreas Schwab
2022-09-11 20:12 ` Sunil Pandey
2022-09-11 20:15 ` Arjan van de Ven
2022-09-11 21:26 ` Florian Weimer
2022-09-29 0:09 ` Noah Goldstein
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