From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by sourceware.org (Postfix) with ESMTPS id 66F103858D32; Sun, 11 Sep 2022 20:15:17 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 66F103858D32 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=linux.intel.com Authentication-Results: sourceware.org; spf=none smtp.mailfrom=linux.intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1662927317; x=1694463317; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=XgZGQj20J4dv9zNVHdxaVdFK2LLtNVGQD4AWr1HoRgE=; b=N+xCibcTKNpgazcG2hUmFlsf0JaBUwQiku0snT4pwdv+IEgvUHuyiai5 t88uY+g1UDOFybNLrUpCe0ZNFaIbFtYLdFt/V3K2xDW8FvExX2J+qExzo UcONbOf8h5wxcHzE9QtaBJeXKm1G5FO3cO4HJcyUTjicdibIlSTfb38js 0NOfeTVFs5jHDRgB1ExRon0DexWMkV2dcT1Iu2B7ZgBJktu76QIF7cGEq Bz/tkN5LNViXMNBHoM82NGjLSEJrf6S0VWO2a2PP+vWhPV2UE+ZDvxGx5 EDPUNmJNcjvqytA/oN4ot4G9IWmos1nkCf9nOvmu36nJlmEgxNo1U7gIG Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10467"; a="361702343" X-IronPort-AV: E=Sophos;i="5.93,307,1654585200"; d="scan'208";a="361702343" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2022 13:15:16 -0700 X-IronPort-AV: E=Sophos;i="5.93,307,1654585200"; d="scan'208";a="860946211" Received: from avandeve-mobl.amr.corp.intel.com (HELO [10.209.26.154]) ([10.209.26.154]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2022 13:15:15 -0700 Message-ID: <5ba017f8-b7d3-12a0-4186-d57ff48eac26@linux.intel.com> Date: Sun, 11 Sep 2022 13:15:15 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH v6 4/4] Avoid extra load with CAS in __pthread_mutex_clocklock_common [BZ #28537] To: Sunil Pandey , Andreas Schwab , Libc-stable Mailing List Cc: "H.J. Lu" , Florian Weimer , GNU C Library , "Paul A . Clarke" References: <20211111162428.2286605-1-hjl.tools@gmail.com> <20211111162428.2286605-5-hjl.tools@gmail.com> <87v90xryvi.fsf@igel.home> Content-Language: en-US From: Arjan van de Ven In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-15.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,GIT_PATCH_0,NICE_REPLY_A,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 9/11/2022 1:12 PM, Sunil Pandey wrote: > On Fri, Nov 12, 2021 at 10:53 AM Andreas Schwab wrote: >> >> On Nov 11 2021, H.J. Lu wrote: >> >>> diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c >>> index 57f3f28869..f763cfc7fa 100644 >>> --- a/nptl/pthread_mutex_timedlock.c >>> +++ b/nptl/pthread_mutex_timedlock.c >>> @@ -233,12 +233,12 @@ __pthread_mutex_clocklock_common (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 > what exactly is the stable branch policy that would suggest to backport performance improvements like this ? (most projects are sticking to "strict bugfixes and other gross oversights" as much as possible)