From: Andreas Schwab <schwab@linux-m68k.org>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: libc-alpha@sourceware.org, Florian Weimer <fweimer@redhat.com>,
Oleh Derevenko <oleh.derevenko@gmail.com>,
Arjan van de Ven <arjan@linux.intel.com>,
"Paul A . Clarke" <pc@us.ibm.com>,
Noah Goldstein <goldstein.w.n@gmail.com>
Subject: Re: [PATCH v6 2/4] Avoid extra load with CAS in __pthread_mutex_lock_full [BZ #28537]
Date: Fri, 12 Nov 2021 19:50:50 +0100 [thread overview]
Message-ID: <87zgq9rywl.fsf@igel.home> (raw)
In-Reply-To: <20211111162428.2286605-3-hjl.tools@gmail.com> (H. J. Lu's message of "Thu, 11 Nov 2021 08:24:26 -0800")
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."
next prev parent reply other threads:[~2021-11-12 18:50 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 [this message]
2022-09-11 20:16 ` Sunil Pandey
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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