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=-11.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 5397DC54E4A for ; Tue, 12 May 2020 14:37:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3386C206F5 for ; Tue, 12 May 2020 14:37:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730255AbgELOg7 (ORCPT ); Tue, 12 May 2020 10:36:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727109AbgELOg6 (ORCPT ); Tue, 12 May 2020 10:36:58 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C1FDBC061A0E; Tue, 12 May 2020 07:36:58 -0700 (PDT) Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jYW1e-0005lm-2i; Tue, 12 May 2020 16:36:54 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id A495F1C0475; Tue, 12 May 2020 16:36:53 +0200 (CEST) Date: Tue, 12 May 2020 14:36:53 -0000 From: "tip-bot2 for Will Deacon" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: locking/kcsan] READ_ONCE: Use data_race() to avoid KCSAN instrumentation Cc: Will Deacon , Thomas Gleixner , "Peter Zijlstra (Intel)" , Marco Elver , x86 , LKML In-Reply-To: <20200511204150.27858-18-will@kernel.org> References: <20200511204150.27858-18-will@kernel.org> MIME-Version: 1.0 Message-ID: <158929421358.390.2138794300247844367.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the locking/kcsan branch of tip: Commit-ID: cdd28ad2d8110099e43527e96d059c5639809680 Gitweb: https://git.kernel.org/tip/cdd28ad2d8110099e43527e96d059c5639809680 Author: Will Deacon AuthorDate: Mon, 11 May 2020 21:41:49 +01:00 Committer: Thomas Gleixner CommitterDate: Tue, 12 May 2020 11:04:17 +02:00 READ_ONCE: Use data_race() to avoid KCSAN instrumentation Rather then open-code the disabling/enabling of KCSAN across the guts of {READ,WRITE}_ONCE(), defer to the data_race() macro instead. Signed-off-by: Will Deacon Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: Marco Elver Link: https://lkml.kernel.org/r/20200511204150.27858-18-will@kernel.org --- include/linux/compiler.h | 54 +++++++++++++++++---------------------- 1 file changed, 24 insertions(+), 30 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index cb2e3b3..741c93c 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -199,6 +199,26 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #include #include +/** + * data_race - mark an expression as containing intentional data races + * + * This data_race() macro is useful for situations in which data races + * should be forgiven. One example is diagnostic code that accesses + * shared variables but is not a part of the core synchronization design. + * + * This macro *does not* affect normal code generation, but is a hint + * to tooling that data races here are to be ignored. + */ +#define data_race(expr) \ +({ \ + __kcsan_disable_current(); \ + ({ \ + __unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \ + __kcsan_enable_current(); \ + __v; \ + }); \ +}) + /* * Use __READ_ONCE() instead of READ_ONCE() if you do not require any * atomicity or dependency ordering guarantees. Note that this may result @@ -209,14 +229,10 @@ 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)); \ - __kcsan_disable_current(); \ - ({ \ - __unqual_scalar_typeof(x) __x = __READ_ONCE(*__xp); \ - __kcsan_enable_current(); \ - smp_read_barrier_depends(); \ - (typeof(x))__x; \ - }); \ + smp_read_barrier_depends(); \ + (typeof(x))__x; \ }) #define READ_ONCE(x) \ @@ -234,9 +250,7 @@ do { \ do { \ typeof(x) *__xp = &(x); \ kcsan_check_atomic_write(__xp, sizeof(*__xp)); \ - __kcsan_disable_current(); \ - __WRITE_ONCE(*__xp, val); \ - __kcsan_enable_current(); \ + data_race(({ __WRITE_ONCE(*__xp, val); 0; })); \ } while (0) #define WRITE_ONCE(x, val) \ @@ -304,26 +318,6 @@ unsigned long read_word_at_a_time(const void *addr) return *(unsigned long *)addr; } -/** - * data_race - mark an expression as containing intentional data races - * - * This data_race() macro is useful for situations in which data races - * should be forgiven. One example is diagnostic code that accesses - * shared variables but is not a part of the core synchronization design. - * - * This macro *does not* affect normal code generation, but is a hint - * to tooling that data races here are to be ignored. - */ -#define data_race(expr) \ -({ \ - __kcsan_disable_current(); \ - ({ \ - __unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \ - __kcsan_enable_current(); \ - __v; \ - }); \ -}) - #endif /* __KERNEL__ */ /*