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From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Sunil Pandey <skpgkp2@gmail.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>,
	 Libc-stable Mailing List <libc-stable@sourceware.org>,
	Florian Weimer <fweimer@redhat.com>,
	 Arjan van de Ven <arjan@linux.intel.com>,
	GNU C Library <libc-alpha@sourceware.org>,
	 "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: Wed, 28 Sep 2022 20:10:57 -0400	[thread overview]
Message-ID: <CAFUsyfJGvPfUSi9N8V=TAN527hWVfaEfFh-WXgD6rKUPA6bRZw@mail.gmail.com> (raw)
In-Reply-To: <CAMAf5_d+Q1e6AWdhzi5d0LaV1et6a6RNLbo+c_mYnt5Gm43-gA@mail.gmail.com>

On Sun, Sep 11, 2022 at 4:17 PM Sunil Pandey via Libc-stable
<libc-stable@sourceware.org> wrote:
>
> 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>

Fine by me.

  reply	other threads:[~2022-09-29  0:11 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20211111162428.2286605-1-hjl.tools@gmail.com>
     [not found] ` <20211111162428.2286605-5-hjl.tools@gmail.com>
     [not found]   ` <87v90xryvi.fsf@igel.home>
2022-09-11 20:12     ` [PATCH v6 4/4] Avoid extra load with CAS in __pthread_mutex_clocklock_common " 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
     [not found] ` <20211111162428.2286605-3-hjl.tools@gmail.com>
     [not found]   ` <87zgq9rywl.fsf@igel.home>
2022-09-11 20:16     ` [PATCH v6 2/4] Avoid extra load with CAS in __pthread_mutex_lock_full " Sunil Pandey
2022-09-29  0:10       ` Noah Goldstein [this message]
     [not found] ` <20211111162428.2286605-2-hjl.tools@gmail.com>
     [not found]   ` <CAFUsyfJH45MshHkFjohENvhJzt1bC=PrUH_3xRn1KubGy9X1HA@mail.gmail.com>
     [not found]     ` <CAMe9rOqOv3WC9rWwtFyzc7rJFDDbNTAfTio-FZC4oW5y751FWA@mail.gmail.com>
     [not found]       ` <CAFUsyf+Yf=QM-0Zj31=k6fANCdXa6XnzVn=Kj6im3xDYbanbnA@mail.gmail.com>
     [not found]         ` <CAMe9rOpE1+1zqtA4xqJNy-RK03jXNzv-JnYSJFtGmtqSa2QqQQ@mail.gmail.com>
     [not found]           ` <924a80cd-202c-99e9-a2d9-1aeda2235b83@linux.intel.com>
2022-09-11 20:19             ` [PATCH v6 1/4] Add LLL_MUTEX_READ_LOCK " Sunil Pandey
2022-09-29  0:10               ` Noah Goldstein

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