From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-13.3 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 7AA3D7D917 for ; Thu, 14 Nov 2019 18:05:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727314AbfKNSEH (ORCPT ); Thu, 14 Nov 2019 13:04:07 -0500 Received: from mail-qv1-f73.google.com ([209.85.219.73]:35026 "EHLO mail-qv1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727301AbfKNSEG (ORCPT ); Thu, 14 Nov 2019 13:04:06 -0500 Received: by mail-qv1-f73.google.com with SMTP id d3so1571381qvz.2 for ; Thu, 14 Nov 2019 10:04:04 -0800 (PST) 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=c5ZdhZ0YGUmz1p5pK6AEd80tJtC02zu3w0ESO5REMCw=; b=HvmXn12wl0qX/E3Rsy6XqFvz7iTSNFZJIf1ZuTbKx3Tf8RzcRepEE5HIoqTt7DRQTD BhA9D84TWAiMyyFx8ULMX+Dm3fgOaUFKhbkkAo23XPCj17yXfdvGlxXC3T5hbr6vY+2E /+LOp1OCb1YMNQGDPTs/kvDX3vj+tn43TQfV5DRowqaLe3Rsy0CJONrwytkRB963xQt2 RhDiCzHw1wa4bGdIbJDAOtNuLIelDK4ow+jKCLXn6s6/F6/Dqiq3o5xn1VqYsLMdgaay aADxdgs93rup9XUu0H6SUFQRc26NJEOqN8mzXO6Y75vGKv4cuA3T/r8IkQiHZQ5uN5h2 exoA== 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=c5ZdhZ0YGUmz1p5pK6AEd80tJtC02zu3w0ESO5REMCw=; b=b/60BYdB2O+eA48SKHl9ycvX29un3+s4xPJyD6RoYDLNgkOtCSd5WBBmiBHCiPasNY h++K5LsN6fuWbc/JKpdi+HNmKpR5scJVc11subZatZ76S2+3lq6x04wfTGKVMjmyr9Gf saman87yE9BVl6rDYBsDgxHjx8mFl44nmQ6l+MdUf8CMhfW9lrjvzhBqymNqI8CWV++b ISWUee9owJEXv0Pc7YNLqsn9RtCrMFmx+Kro7jMlDb6aZLFrEKqhEbc50obUcEhBpt2q p9sZTksyPhcpz9yH6ahziEwZO7dMT42/moXizomM/HOfIEEQm+05pAx5nnEP92Z3oivD RXTw== X-Gm-Message-State: APjAAAWK7Rh2tAAfyRf1pZJ2gVJlMpuP60CYv1aE2mGYNSb+zeHbZ2Ss soaa/4Dxt/3/mYscHdKNuHWnqL5Gvw== X-Google-Smtp-Source: APXvYqwUlw4hUlsakl9iLIPewvS2JHArNK+4NJ+usYinBWA3JzGZ7XeylKBeWUNZaEF3evwOmxW2Hl7CfA== X-Received: by 2002:a05:6214:1332:: with SMTP id c18mr7908552qvv.213.1573754643719; Thu, 14 Nov 2019 10:04:03 -0800 (PST) Date: Thu, 14 Nov 2019 19:02:55 +0100 In-Reply-To: <20191114180303.66955-1-elver@google.com> Message-Id: <20191114180303.66955-3-elver@google.com> Mime-Version: 1.0 References: <20191114180303.66955-1-elver@google.com> X-Mailer: git-send-email 2.24.0.rc1.363.gb1bccd3e3d-goog Subject: [PATCH v4 02/10] include/linux/compiler.h: Introduce data_race(expr) macro From: Marco Elver To: elver@google.com Cc: akiyks@gmail.com, stern@rowland.harvard.edu, glider@google.com, parri.andrea@gmail.com, andreyknvl@google.com, luto@kernel.org, ard.biesheuvel@linaro.org, arnd@arndb.de, boqun.feng@gmail.com, bp@alien8.de, dja@axtens.net, dlustig@nvidia.com, dave.hansen@linux.intel.com, dhowells@redhat.com, dvyukov@google.com, hpa@zytor.com, mingo@redhat.com, j.alglave@ucl.ac.uk, joel@joelfernandes.org, corbet@lwn.net, jpoimboe@redhat.com, luc.maranget@inria.fr, mark.rutland@arm.com, npiggin@gmail.com, paulmck@kernel.org, peterz@infradead.org, tglx@linutronix.de, will@kernel.org, edumazet@google.com, kasan-dev@googlegroups.com, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-efi@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, Linus Torvalds Content-Type: text/plain; charset="UTF-8" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org This introduces the data_race(expr) macro, which can be used to annotate expressions for purposes of (1) documenting, and (2) giving tooling such as KCSAN information about which data races are deemed "safe". More context: http://lkml.kernel.org/r/CAHk-=wg5CkOEF8DTez1Qu0XTEFw_oHhxN98bDnFqbY7HL5AB2g@mail.gmail.com Signed-off-by: Marco Elver Cc: Alan Stern Cc: Eric Dumazet Cc: Linus Torvalds Cc: Paul E. McKenney --- v4: * Introduce this patch to KCSAN series. --- include/linux/compiler.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index c42fa83f23fb..7d3e77781578 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -310,6 +310,26 @@ unsigned long read_word_at_a_time(const void *addr) __u.__val; \ }) +#include + +/* + * data_race: macro to document that accesses in an expression may conflict with + * other concurrent accesses resulting in data races, but the resulting + * behaviour is deemed safe regardless. + * + * This macro *does not* affect normal code generation, but is a hint to tooling + * that data races here should be ignored. + */ +#define data_race(expr) \ + ({ \ + typeof(({ expr; })) __val; \ + kcsan_nestable_atomic_begin(); \ + __val = ({ expr; }); \ + kcsan_nestable_atomic_end(); \ + __val; \ + }) +#else + #endif /* __KERNEL__ */ /* -- 2.24.0.rc1.363.gb1bccd3e3d-goog