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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 C61E1C433E1 for ; Tue, 21 Jul 2020 14:34:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A230C206E3 for ; Tue, 21 Jul 2020 14:34:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QdO/VkrL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729031AbgGUOem (ORCPT ); Tue, 21 Jul 2020 10:34:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55142 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726412AbgGUOel (ORCPT ); Tue, 21 Jul 2020 10:34:41 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43D3CC061794; Tue, 21 Jul 2020 07:34:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=awvO/AxzZMb5RICr1smsNlHEgfMyuxuSrzQI8mKeLw0=; b=QdO/VkrL9Ut3AyXGXc0eOxFwZf ydHUDTMC0Sz0h8xQjhpBJVcOhUGVHhOy655jDK/cQtB4ES3xAREo1eJbUmQ5/HyJlPVUtUddajOG7 NUg5n96enPPuq7Q/+xgrA1/hZ89vAvsqyTGvbmZGLAcaRVflMKjWRy1dfJJ9dpzlpI4MIT55qCuIb XVwaqFVRBhNxhDapqdfK9kQV9kEhj/bQkVmNMZa2lKZJM0QpRzIgzfTotGsXnrxSuNt6hlx5zm7B0 6uyUxL3pDvnjud42NM+WbGO+DV8+X9MV2P/zrTlN37w4desmyvBzjfuBj96iRFWN5IaSY7UZgAiAB gszf8JbQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jxtLl-0002ZX-ID; Tue, 21 Jul 2020 14:34:33 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 5FE973011C6; Tue, 21 Jul 2020 16:34:32 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 24B9C25E22790; Tue, 21 Jul 2020 16:34:32 +0200 (CEST) Date: Tue, 21 Jul 2020 16:34:32 +0200 From: peterz@infradead.org To: Marco Elver Cc: paulmck@kernel.org, will@kernel.org, arnd@arndb.de, mark.rutland@arm.com, dvyukov@google.com, glider@google.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 3/8] kcsan: Skew delay to be longer for certain access types Message-ID: <20200721143432.GM119549@hirez.programming.kicks-ass.net> References: <20200721103016.3287832-1-elver@google.com> <20200721103016.3287832-4-elver@google.com> <20200721140523.GA10769@hirez.programming.kicks-ass.net> <20200721142654.GA3396394@elver.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200721142654.GA3396394@elver.google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 21, 2020 at 04:26:54PM +0200, Marco Elver wrote: > I'll rewrite the commit message: > > For compound instrumentation and assert accesses, skew the > watchpoint delay to be longer if randomized. This is useful to > improve race detection for such accesses. > > For compound accesses we should increase the delay as we've > aggregated both read and write instrumentation. By giving up 1 > call into the runtime, we're less likely to set up a watchpoint > and thus less likely to detect a race. We can balance this by > increasing the watchpoint delay. Aah, makes sense now. Thanks!