From mboxrd@z Thu Jan 1 00:00:00 1970 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 C7D45C433EF for ; Wed, 25 May 2022 14:40:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242428AbiEYOkd (ORCPT ); Wed, 25 May 2022 10:40:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231761AbiEYOkZ (ORCPT ); Wed, 25 May 2022 10:40:25 -0400 Received: from mail-ej1-x62e.google.com (mail-ej1-x62e.google.com [IPv6:2a00:1450:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B6399326E5 for ; Wed, 25 May 2022 07:40:24 -0700 (PDT) Received: by mail-ej1-x62e.google.com with SMTP id jx22so28687929ejb.12 for ; Wed, 25 May 2022 07:40:24 -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=CLjQF+Tk2Dzg/+o3qFGpi4ZRr2G7ec0w/EcVuau6V3o=; b=gNP79hxx2bGKSSokzC/ujzec2WuXtVPOMlNGUx6axODqSxaeUuQThaQXqkJWd9ShqS nCjDFv30ZMjMfJ1iIsYpUOkda+HM2Qu4QFCzxP0b3w2Wx6t7T8ZSWL0eIGND8IRKDB/1 /e0bq53RAXlWgk28rxW6UuGBVKBCuQXdjaFQRLXmJkYyH0H+YNZvKUXSeu2rSOOuvZ9O JholRfIWHOz5KIhrmwwJ7gCFRtcVK90lHQpqN+EVd7yYC5ocyiig52ny8obY7yhd94vf AfTIxpsnVHTY48Dqu23sM1S47Ao7Qv6gHTdoeMdCoIUk0FM8uPLfB1G766bQ/as80z6m zvIQ== 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=CLjQF+Tk2Dzg/+o3qFGpi4ZRr2G7ec0w/EcVuau6V3o=; b=q7fNVfOwuy1t0IoMX5iV6bQkP8mHpy3N5gsrreXmdQIbZaBc2PB5oscfzzJ6Cl2MRn Hsv3nL8h5II6yoi5YkmKPYHSCvai70R3MBpIR0g+UFXjcfdRc2gL7CJ57kv3sS/Ezoly 8wD+yj9mhRYnd++2dwpwX6zjpkJyzXX4/0SUh5HuHQBmnweUGsnYVF22eHMt8SOrYrnJ 1mNvjK5pSh3v3auONxLdhKxC5/bVQVqT3pQRF1+IgUKxaQzRwDnMl5zX0MViz6of7T3C YizOZHhM3qA8/3Qx9RrSbZqWh3Pv1wbdqy854esboUSGx/SaSSeRdKD65JZ1obJxEg6p oIIg== X-Gm-Message-State: AOAM532UDks3hjZ9kLM+iDPYsHzwuK3jqykk6dm7Y8c1LGvsl+horwXu PTPcynPXMs0yCTqRp0ZXCu4= X-Google-Smtp-Source: ABdhPJxxpyp3+790QyGn2MuWx/D1L+faCOhc9lYzD23MnLAmKwkFiYUVUoMVVxHcPCHtBTYO7t4dyg== X-Received: by 2002:a17:907:7745:b0:6f3:674a:339 with SMTP id kx5-20020a170907774500b006f3674a0339mr29675341ejc.207.1653489623224; Wed, 25 May 2022 07:40:23 -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 4-20020a170906224400b006f3ef214da7sm8288262ejr.13.2022.05.25.07.40.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 May 2022 07:40:22 -0700 (PDT) From: Uros Bizjak To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Waiman.Long@hp.com, paulmck@linux.vnet.ibm.com Subject: [PATCH 0/2] locking/lockref: Use try_cmpxchg64 in CMPXCHG_LOOP macro Date: Wed, 25 May 2022 16:40:11 +0200 Message-Id: <20220525144013.6481-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch series introduces try_cmpxchg64 into CMPXCHG_LOOP macro to improve generated code a bit. x86 CMPXCHG instruction returns success in ZF flag, so a compare after CMPXCHG and a related move instruction can be eliminated. The second patch (optionally) enables lockless reference count updates for X86_32 target with X86_CMPXCHG64 config flag set. When try_cmpxchg64 is used in CMPXCHG_LOOP macro in lib/lockref.c, the compiler avoids double-word compare and related move and produces quite optimal code around CMPXCHG8B for a register starved X86_32 target. Signed-off-by: Uros Bizjak Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Waiman.Long@hp.com Cc: paulmck@linux.vnet.ibm.com --- Uros Bizjak (2): locking/lockref: Use try_cmpxchg64 in CMPXCHG_LOOP macro locking/lockref/x86: Enable ARCH_USE_CMPXCHG_LOCKREF for X86_32 && X86_CMPXCHG64 arch/x86/Kconfig | 2 +- lib/lockref.c | 9 ++++----- 2 files changed, 5 insertions(+), 6 deletions(-) -- 2.35.3