From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 7852) id E58BD3858D28; Thu, 29 Sep 2022 00:47:53 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E58BD3858D28 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1664412473; bh=COhXDKpZ8uEF5y4tWVb7lJU2WBz/5/2oVhatWsuKZDY=; h=From:To:Subject:Date:From; b=XAL5oXwxa1Ihddv0NSxnWdXSpmlHR7xIpxopmWqYPFI7yWR/2h0WiAk6uJkeN5xzE /ND5UW7NCwFPdvfCsXGbW9GfiCy0zdSPJYZSwzKLvpC+BX3wtnxqu6G8yAKl34JI5V YqLdJl3aYTU6JmAXUXxv8L5OdJh7Fd44AjWRmQRw= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Sunil Pandey To: glibc-cvs@sourceware.org Subject: [glibc/release/2.33/master] Avoid extra load with CAS in __pthread_mutex_lock_full [BZ #28537] X-Act-Checkin: glibc X-Git-Author: H.J. Lu X-Git-Refname: refs/heads/release/2.33/master X-Git-Oldrev: da7afc97ad9ddc817686d61f046277166ef42644 X-Git-Newrev: f5a70409db67f3a5f035d9d6082d11efcc74910d Message-Id: <20220929004753.E58BD3858D28@sourceware.org> Date: Thu, 29 Sep 2022 00:47:53 +0000 (GMT) List-Id: https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f5a70409db67f3a5f035d9d6082d11efcc74910d commit f5a70409db67f3a5f035d9d6082d11efcc74910d Author: H.J. Lu 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. Reviewed-by: Szabolcs Nagy (cherry picked from commit 0b82747dc48d5bf0871bdc6da8cb6eec1256355f) Diff: --- nptl/pthread_mutex_lock.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c index 319658adc4..0fd7467b97 100644 --- a/nptl/pthread_mutex_lock.c +++ b/nptl/pthread_mutex_lock.c @@ -289,12 +289,12 @@ __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) { - oldval = mutex->__data.__lock; + oldval = val; continue; } oldval |= FUTEX_WAITERS;