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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 930E3C2BA19 for ; Wed, 15 Apr 2020 19:08:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A21120768 for ; Wed, 15 Apr 2020 19:08:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586977728; bh=uRBIJ6sd0gcFbtrSkv57SfMJWDHOcqP+JtoufcputUo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=1+BeW3PfT1+b7sbfLo12z05ZbHIOLayhtqVgs7s83G1c8hgeErNo+Lt071teXV52k 6/SX7nSnl96HnzhvMCSEfi20M/amK76aCwobawkkKNxMJAsIO1lCJ8INsh2UpflRWt lViLdIGCuIrDyyyktrZV314EVdM9LJdSfrgrrbP4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2441562AbgDOTIn (ORCPT ); Wed, 15 Apr 2020 15:08:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:42478 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1416823AbgDOSeR (ORCPT ); Wed, 15 Apr 2020 14:34:17 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 57D3721655; Wed, 15 Apr 2020 18:34:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586975656; bh=uRBIJ6sd0gcFbtrSkv57SfMJWDHOcqP+JtoufcputUo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g9gpm3SVTpAKT3TXayFYQ4tINFhkZS8cGnIHPwsLoxvRcWXniN6AZkpAVzNYLRo8d qb31Kger5Sm5gvv8AShOKSV3QGk68dD38abhGe18p4XVE0dwEQDzAiQcv0ucCRSt7K FHslLNg+9TShr0sLvhbQE0hoGI/vLo0dkROHHJL0= From: paulmck@kernel.org To: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, kernel-team@fb.com, mingo@kernel.org Cc: elver@google.com, andreyknvl@google.com, glider@google.com, dvyukov@google.com, cai@lca.pw, boqun.feng@gmail.com, "Paul E . McKenney" , Will Deacon Subject: [PATCH v4 tip/core/rcu 13/15] kcsan: Change data_race() to no longer require marking racing accesses Date: Wed, 15 Apr 2020 11:34:09 -0700 Message-Id: <20200415183411.12368-13-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200415183343.GA12265@paulmck-ThinkPad-P72> References: <20200415183343.GA12265@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Marco Elver Thus far, accesses marked with data_race() would still require the racing access to be marked in some way (be it with READ_ONCE(), WRITE_ONCE(), or data_race() itself), as otherwise KCSAN would still report a data race. This requirement, however, seems to be unintuitive, and some valid use-cases demand *not* marking other accesses, as it might hide more serious bugs (e.g. diagnostic reads). Therefore, this commit changes data_race() to no longer require marking racing accesses (although it's still recommended if possible). The alternative would have been introducing another variant of data_race(), however, since usage of data_race() already needs to be carefully reasoned about, distinguishing between these cases likely adds more complexity in the wrong place. Link: https://lkml.kernel.org/r/20200331131002.GA30975@willie-the-truck Cc: Paul E. McKenney Cc: Will Deacon Cc: Qian Cai Acked-by: Will Deacon Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- include/linux/compiler.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index f504ede..1729bd1 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -326,9 +326,9 @@ unsigned long read_word_at_a_time(const void *addr) #define data_race(expr) \ ({ \ typeof(({ expr; })) __val; \ - kcsan_nestable_atomic_begin(); \ + kcsan_disable_current(); \ __val = ({ expr; }); \ - kcsan_nestable_atomic_end(); \ + kcsan_enable_current(); \ __val; \ }) #else -- 2.9.5