From patchwork Tue Dec 14 12:30:51 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: 48895 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 C0C213858411 for ; Tue, 14 Dec 2021 12:31:28 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C0C213858411 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1639485088; bh=NtidRKagj/RqV+0b5ppNLydRADoly3plQ6EtHgGVP8g=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=wedJp1vnyyibtJc5IrXUUWWgtJ1P7xYGW+ZpjaQVcXfp+IEZfu9TnJy4SRU6ysBrx 6QtW5HrxYIDgZzUsfXoJqMcEwshWvGxeRXvSU1xej2hTNn4fvOSeK/YNyVE0Q2Mur0 nXxWR4ah57zO9yKngCGrHZ/3JwiIXGLuG1+arKzY= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by sourceware.org (Postfix) with ESMTPS id 44BC53858D28 for ; Tue, 14 Dec 2021 12:31:07 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 44BC53858D28 Received: by mail-pj1-x102f.google.com with SMTP id n15-20020a17090a394f00b001b0f6d6468eso570849pjf.3 for ; Tue, 14 Dec 2021 04:31:07 -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=NtidRKagj/RqV+0b5ppNLydRADoly3plQ6EtHgGVP8g=; b=nWfKvPS6GjrKIuEDwGt/J6JN4tvupGQagN+X5PV6TrCr9khZZKiHm7DllFXLvyz+k8 G/T3GEHf2F348CDUFo0kMObIsRRZBSITJIL5zBwPl/0nF57Om/QWGAsLKm9sWXTg66ts GyzjLANbJm1DpeW2KGwkaXGS9LHq/ReJ/N1wrvXHAb+RMn5rqI7/K6QtCbEpWAnOR8Xs EwuZWTbbzqirUlqfT9QlNTLpa+rbJDshzXw8+UcMfTAMTe1tPQE094NtciFrGeWPatMv 1Dcko1HVt1WrysNd9fNXLtHWl6BDc0oEZZMCl2aNtvPlKWMXNEShG7No7aSDQ3a9yagf O6Fw== X-Gm-Message-State: AOAM532xU8cRJqlTvuK9OJwhPsR0HujsqSygL5AwGrusj5YD4eVaSir0 DGdT2PuMYcmUj0NXXq4GxBO35orrR2+3mQ== X-Google-Smtp-Source: ABdhPJye5v4OYquXIN4iCROmM5VALYdVqehNyrg31FZA85Rhz9KETGR5VFAQeEzqesP0lqbNEhJurw== X-Received: by 2002:a17:90b:4a47:: with SMTP id lb7mr5481283pjb.243.1639485065800; Tue, 14 Dec 2021 04:31:05 -0800 (PST) Received: from DESKTOP-OO3QD6O.localdomain ([221.162.118.197]) by smtp.gmail.com with ESMTPSA id u22sm16550117pfi.187.2021.12.14.04.31.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Dec 2021 04:31:05 -0800 (PST) To: libc-alpha@sourceware.org Subject: [PATCH v3] nptl: Effectively skip CAS in spinlock loop Date: Tue, 14 Dec 2021 21:30:51 +0900 Message-Id: <20211214123051.800-1-6812skiii@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 atomic 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 skip LLL_MUTEX_TRYLOCK if LLL_MUTEX_READ_LOCK fails. Reviewed-by: H.J. Lu --- nptl/pthread_mutex_lock.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c index 47b88a6b5b..06274c68e4 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 (LLL_MUTEX_READ_LOCK (mutex) != 0 || LLL_MUTEX_TRYLOCK (mutex) != 0) { if (cnt++ >= max_cnt) { @@ -146,10 +146,7 @@ PTHREAD_MUTEX_LOCK (pthread_mutex_t *mutex) break; } atomic_spin_nop (); - if (LLL_MUTEX_READ_LOCK (mutex) != 0) - continue; } - while (LLL_MUTEX_TRYLOCK (mutex) != 0); mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8; }