From nobody Thu May 7 20:49:47 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A98F5C433F5 for ; Wed, 18 May 2022 18:50:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241641AbiERSuS (ORCPT ); Wed, 18 May 2022 14:50:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241624AbiERSuO (ORCPT ); Wed, 18 May 2022 14:50:14 -0400 Received: from mail-ej1-x635.google.com (mail-ej1-x635.google.com [IPv6:2a00:1450:4864:20::635]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E8732EA17 for ; Wed, 18 May 2022 11:50:13 -0700 (PDT) Received: by mail-ej1-x635.google.com with SMTP id ck4so1275885ejb.8 for ; Wed, 18 May 2022 11:50:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=pqI2+xUvKnWcIdSP6yP4fejkeLxIn1EuNN3syEENFFE=; b=ku0RmPMoWqvIQqEw7XKved+GSKuUfRade7blj4kfDUDuPWoOiPGgOjCbSoHSzCn9R6 S+HsJ3PMaJ9qIpGRIkp7qCyCRFU5BjNDyAeg9M0u315lzErTSZ/wqPxH6ibHPU65aM6r xhnKdhx7o+yN4xzdu+2R62ATJrYY/NZYGtfSmZWP0EYGzEpvzlfiaVrk5/0FP8bYyv0t s6yPe5UT6mwoaKnLahx7w0IotyxuMnwFWjjF9Kt5LZjjFnx8mafw3rso8GVCTkIR7oSY YadjW6svAKOLhv8NH/AhtzAPr4a3lOTFpDZrNSYuy+FGoHayRF2qqEAMQMbNwhzAho+X vlkA== 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=pqI2+xUvKnWcIdSP6yP4fejkeLxIn1EuNN3syEENFFE=; b=l3s85XCc7vtiB5ADlOHlwhMnSI+d3WpaPxy7iDFboDtcoVlj7dfTOVN3rld23u8tjh pqcvCWc4bNzWUcyf7FGwnvY6vjwWn0xSRsxqH0d8y9hhx5HafvXD+rJVZqGklPfEWZTr YWkiBk3uWFhKRC6U89eqOIsO5UJoz7kbYKKoIINsEZ9lsPcgHVKHiIw/pTIWrLa84JH0 aMs/Z82KeF16epJTqXNyFxQPeXJNamrD+/TqCeZkilmB/ssuBpnPkudqwOAjgzHnKZy1 aqTPILad1/jXh8mUbMJVsa8j+HiSaN7GTNU1JaegrEFeEEwhGopwyws6S6TSbY91TPiz svPg== X-Gm-Message-State: AOAM5310gCmh9WsrRBCMVIwamc44XzjEFL41OAh4Ha9XRRZwinC3qakE 4OU3+igEXnc1jXwtg28zGGTuxAPqDn1/kw== X-Google-Smtp-Source: ABdhPJwVRPW7HZvyZ26jxm0P3qXxTBvjoAoK5+NSeQQ+iz1Mg9/hFPy50tr8cQrpXctlskSrLqzFYA== X-Received: by 2002:a17:907:1b0c:b0:6fe:25bf:b3e5 with SMTP id mp12-20020a1709071b0c00b006fe25bfb3e5mr844547ejc.689.1652899811358; Wed, 18 May 2022 11:50:11 -0700 (PDT) Received: from localhost.localdomain (93-103-18-160.static.t-2.net. [93.103.18.160]) by smtp.gmail.com with ESMTPSA id 4-20020a170906008400b006fe8a4ec62fsm961343ejc.4.2022.05.18.11.50.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 May 2022 11:50:10 -0700 (PDT) From: Uros Bizjak To: linux-kernel@vger.kernel.org Cc: Uros Bizjak , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira Subject: [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Date: Wed, 18 May 2022 20:49:53 +0200 Message-Id: <20220518184953.3446778-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) !=3D old in sched_clock_{local,remote}. x86 cmpxchg returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Signed-off-by: Uros Bizjak Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira --- Patch requires commits 0aa7be05d83cc584da0782405e8007e351dfb6cc and c2df0a6af177b6c06a859806a876f92b072dc624 from tip.git --- kernel/sched/clock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index d9272d9061a3..e374c0c923da 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -287,7 +287,7 @@ notrace static u64 sched_clock_local(struct sched_clock= _data *scd) clock =3D wrap_max(clock, min_clock); clock =3D wrap_min(clock, max_clock); =20 - if (cmpxchg64(&scd->clock, old_clock, clock) !=3D old_clock) + if (!try_cmpxchg64(&scd->clock, &old_clock, clock)) goto again; =20 return clock; @@ -349,7 +349,7 @@ notrace static u64 sched_clock_remote(struct sched_cloc= k_data *scd) val =3D remote_clock; } =20 - if (cmpxchg64(ptr, old_val, val) !=3D old_val) + if (!try_cmpxchg64(ptr, &old_val, val)) goto again; =20 return val; --=20 2.35.1