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 X-Spam-Level: X-Spam-Status: No, score=-22.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24E19C433E0 for ; Thu, 21 May 2020 14:22:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EAE1D207F7 for ; Thu, 21 May 2020 14:22:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="L/OPRcba" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729678AbgEUOWp (ORCPT ); Thu, 21 May 2020 10:22:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53740 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729642AbgEUOWj (ORCPT ); Thu, 21 May 2020 10:22:39 -0400 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84A38C061A0E for ; Thu, 21 May 2020 07:22:39 -0700 (PDT) Received: by mail-qv1-xf4a.google.com with SMTP id d11so7271790qvv.10 for ; Thu, 21 May 2020 07:22:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=dz729bx1Pa1pF4PgJy0kCf9Utra9WlCLoUyt1P9z0sg=; b=L/OPRcbazaq2P9GdeWFRmzgC6CARW2S10o2GP4Xoc0hpLGF/m1w2gH3BdB1duH0rSk sHAwprxdsCCmFioPdDgpxk0E5/yt0J/C6W/7iV5w5rc4ZUJWWSeeK6oLUlwRSoAllKx5 nxfbcZ60Fiwd0HdsUSl7BnwCdZARDaF1kZH9fYF6gCzZj3ApA9kTCiKVIEZwjv1yz+Hi 1TRjvV3CbThMI3qbE+RIJGtER4bV9kKcmEXMH3X6+Rz/EtH9HnQyr2qIjpcuHfMHerTq a6mjBK8NbmzylHaCc+BzFKu+j2DUGfMv0jz2u/fGfX+spoo79HqF//GT2hFMBQ8M1w6u lZnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=dz729bx1Pa1pF4PgJy0kCf9Utra9WlCLoUyt1P9z0sg=; b=VJ0KdBvGjAl06iMLnwxQReGe9UfbMnT77f/oPy4I6/se1oFyPLfLySEnHb9hHy+ueE BUtixSCCEVJasi1rd71TxPCAqRjDPjq8p/YY8sC7nosUv1dIo/5PQ1PWtnY0l8vTmL/l zT8DIlvvomcUV8q1qK8UPrq/vBPPGR/z7PRXpvZt9+iCw2Ds+/abknsv8nA1hxYsO/yY +0SzR2hS3Ya58Z1Kpl9fWf8OfCJR4FLYSCA75hpJX24ShUO7I+hwJ77hpvAnxejz1Jb/ GWMDoN0hlNBU5HUfyusCakVNS0UlMlTDJSOR82EJFYo9yAPe2EhLg1iTF3/7WiDH7j2n AxHA== X-Gm-Message-State: AOAM533KynB0e1O1vFcDDFD3HLMCaZuoETyF1PJWBBgF+ITSS9vEZQjt aa3HYyXyLj8xo3sKpDXHrcH8BdKYhg== X-Google-Smtp-Source: ABdhPJwA6KstpYMq2Y70Qwk2d3mwXfEyfhyxA40V03sD+gaGWmNjEwXC9DB9mIBY5YVcXWzq4c4LpXZ7ww== X-Received: by 2002:a0c:c991:: with SMTP id b17mr9979723qvk.16.1590070958659; Thu, 21 May 2020 07:22:38 -0700 (PDT) Date: Thu, 21 May 2020 16:20:44 +0200 In-Reply-To: <20200521142047.169334-1-elver@google.com> Message-Id: <20200521142047.169334-9-elver@google.com> Mime-Version: 1.0 References: <20200521142047.169334-1-elver@google.com> X-Mailer: git-send-email 2.26.2.761.g0e0b3e54be-goog Subject: [PATCH -tip v3 08/11] READ_ONCE, WRITE_ONCE: Remove data_race() and unnecessary checks From: Marco Elver To: elver@google.com Cc: paulmck@kernel.org, dvyukov@google.com, glider@google.com, andreyknvl@google.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, will@kernel.org, clang-built-linux@googlegroups.com, bp@alien8.de Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The volatile accesses no longer need to be wrapped in data_race(), because we require compilers that emit instrumentation distinguishing volatile accesses. Consequently, we also no longer require the explicit kcsan_check_atomic*(), since the compiler emits instrumentation distinguishing the volatile accesses. Finally, simplify __READ_ONCE_SCALAR and remove __WRITE_ONCE_SCALAR. Acked-by: Will Deacon Signed-off-by: Marco Elver --- v2: * Remove unnecessary kcsan_check_atomic*() in *_ONCE. * Simplify __READ_ONCE_SCALAR and remove __WRITE_ONCE_SCALAR. This effectively restores Will Deacon's pre-KCSAN version: https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/tree/include/linux/compiler.h?h=rwonce/cleanup#n202 --- include/linux/compiler.h | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 17c98b215572..7444f026eead 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -228,9 +228,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #define __READ_ONCE_SCALAR(x) \ ({ \ - typeof(x) *__xp = &(x); \ - __unqual_scalar_typeof(x) __x = data_race(__READ_ONCE(*__xp)); \ - kcsan_check_atomic_read(__xp, sizeof(*__xp)); \ + __unqual_scalar_typeof(x) __x = __READ_ONCE(x); \ smp_read_barrier_depends(); \ (typeof(x))__x; \ }) @@ -246,17 +244,10 @@ do { \ *(volatile typeof(x) *)&(x) = (val); \ } while (0) -#define __WRITE_ONCE_SCALAR(x, val) \ -do { \ - typeof(x) *__xp = &(x); \ - kcsan_check_atomic_write(__xp, sizeof(*__xp)); \ - data_race(({ __WRITE_ONCE(*__xp, val); 0; })); \ -} while (0) - #define WRITE_ONCE(x, val) \ do { \ compiletime_assert_rwonce_type(x); \ - __WRITE_ONCE_SCALAR(x, val); \ + __WRITE_ONCE(x, val); \ } while (0) #ifdef CONFIG_KASAN -- 2.26.2.761.g0e0b3e54be-goog