From: Andreas Schwab <schwab@linux-m68k.org>
To: Jangwoong Kim via Libc-alpha <libc-alpha@sourceware.org>
Cc: Jangwoong Kim <6812skiii@gmail.com>
Subject: Re: [PATCH v2] nptl: Effectively skip CAS in spinlock loop
Date: Tue, 14 Dec 2021 12:42:58 +0100 [thread overview]
Message-ID: <87wnk72z0d.fsf@igel.home> (raw)
In-Reply-To: <20211214110119.592-1-6812skiii@gmail.com> (Jangwoong Kim via Libc-alpha's message of "Tue, 14 Dec 2021 20:01:19 +0900")
On Dez 14 2021, Jangwoong Kim via Libc-alpha wrote:
> diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
> index 47b88a6b5b..3ad199a5e1 100644
> --- a/nptl/pthread_mutex_lock.c
> +++ b/nptl/pthread_mutex_lock.c
> @@ -138,7 +138,7 @@ PTHREAD_MUTEX_LOCK (pthread_mutex_t *mutex)
> int cnt = 0;
> int max_cnt = MIN (max_adaptive_count (),
> mutex->__data.__spins * 2 + 10);
> - do
> + while (1)
> {
> if (cnt++ >= max_cnt)
> {
> @@ -146,10 +146,9 @@ PTHREAD_MUTEX_LOCK (pthread_mutex_t *mutex)
> break;
> }
> atomic_spin_nop ();
> - if (LLL_MUTEX_READ_LOCK (mutex) != 0)
> - continue;
> + if (LLL_MUTEX_READ_LOCK (mutex) == 0 && LLL_MUTEX_TRYLOCK (mutex) == 0)
> + break;
> }
> - while (LLL_MUTEX_TRYLOCK (mutex) != 0);
You can keep the condition in the loop trailer.
--
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."
prev parent reply other threads:[~2021-12-14 11:43 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-14 11:01 Jangwoong Kim
2021-12-14 11:42 ` Andreas Schwab [this message]
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