From patchwork Sun Dec 5 15:28:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jangwoong Kim <6812skiii@gmail.com> X-Patchwork-Id: 48513 X-Patchwork-Delegate: maxim.kuvyrkov@gmail.com Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 71CAB3858424 for ; Sun, 5 Dec 2021 15:28:43 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 71CAB3858424 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1638718123; bh=6Zwuvb2vx5TUq9ZyUTUdWxxfI9i124eZ1UFJ1QoIYDM=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=MtN1qNVqq7wUxAFEZVQ/7gBYy4UsVyaESXYO3TV8dg21hZ/em8/shg6I+BZoc62sn 32+NAYmK3FMPswvIvkGKCanFa3cY9eXTQaRu/o6EgMtpCYMzXklR9slz69CbaMNL/k 0hGmkwyeARnWE8Dy0f+kkCTYSbrnDdbGXM5tI8hM= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by sourceware.org (Postfix) with ESMTPS id 8A4DF3858D28 for ; Sun, 5 Dec 2021 15:28:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 8A4DF3858D28 Received: by mail-pj1-x102e.google.com with SMTP id j6-20020a17090a588600b001a78a5ce46aso8932030pji.0 for ; Sun, 05 Dec 2021 07:28:22 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=6Zwuvb2vx5TUq9ZyUTUdWxxfI9i124eZ1UFJ1QoIYDM=; b=dRiUmjvyUiKdCF2qPrAjawL/G1TQBFRtujwyrYFM02xAXl7VQ3r5u7Hks4FipghZoc usQacM4CXpXqiD817ih2j9aVYz4f//uujBw6xLEMzu/oZEPjLIyq7zOZTelzU4fNC0wH +/GeeAAUa1ylJcUquRl1r1RIqdcDc8RWJlbKMX8Bi1qo1rMUDz4tn3Nvyxv3S7PV9/rR 3BQl7GQJWhckX/EIMs3qF6MOg+P8ZAENxBrSHhfECiX4rkYCadbHVyvNgWbuv4ACdddR ti1yFNYNLE6qLXVHkmeiJq2YoCE910OLxtlmUPzIgoq0HMYiGbwmMoV8SFr/4j6Rpr8X a6YA== X-Gm-Message-State: AOAM533FQoh/+adrF+IUb+NL4SCgA01Yjo/46Cb82/m6v0IlXLLklCIS srNf3Q5MeJpbm4lizGLFUoqZZA/1SVY2ww== X-Google-Smtp-Source: ABdhPJxa9mIeYut8VxuStXs1hEStLXxZ/1VvMcZBT1FoKSAi5glL7AMAn35LSidBer3/bzYjfH9YzQ== X-Received: by 2002:a17:90b:4acd:: with SMTP id mh13mr30198021pjb.230.1638718101541; Sun, 05 Dec 2021 07:28:21 -0800 (PST) Received: from DESKTOP-OO3QD6O.localdomain ([221.162.118.197]) by smtp.gmail.com with ESMTPSA id a2sm7390899pgn.20.2021.12.05.07.28.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 05 Dec 2021 07:28:21 -0800 (PST) To: libc-alpha@sourceware.org Subject: [PATCH] nptl: Effectively skip CAS in spinlock loop Date: Mon, 6 Dec 2021 00:28:14 +0900 Message-Id: <20211205152814.13597-1-6812skiii@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Spam-Status: No, score=-12.2 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, FROM_STARTS_WITH_NUMS, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Jangwoong Kim via Libc-alpha From: Jangwoong Kim <6812skiii@gmail.com> Reply-To: Jangwoong Kim <6812skiii@gmail.com> Cc: Jangwoong Kim <6812skiii@gmail.com> Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" The commit: "Add LLL_MUTEX_READ_LOCK [BZ #28537]" SHA1: d672a98a1af106bd68deb15576710cd61363f7a6 introduced LLL_MUTEX_READ_LOCK, to skip CAS in spinlock loop if atmoic load fails. But, "continue" inside of do-while loop does not skip the evaluation of escape expression, thus CAS is not skipped. Replace do-while with while and break if LLL_MUTEX_READ_LOCK fails. --- nptl/pthread_mutex_lock.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c index 47b88a6b5b..24936c8d56 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) { @@ -148,8 +148,9 @@ PTHREAD_MUTEX_LOCK (pthread_mutex_t *mutex) atomic_spin_nop (); if (LLL_MUTEX_READ_LOCK (mutex) != 0) continue; + if (LLL_MUTEX_TRYLOCK (mutex) == 0) + break; } - while (LLL_MUTEX_TRYLOCK (mutex) != 0); mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8; }