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=-13.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 DCCA6C432C3 for ; Fri, 15 Nov 2019 17:15:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD2D920728 for ; Fri, 15 Nov 2019 17:15:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CBFLAcP+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727655AbfKORPB (ORCPT ); Fri, 15 Nov 2019 12:15:01 -0500 Received: from mail-oi1-f196.google.com ([209.85.167.196]:39519 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727625AbfKORPA (ORCPT ); Fri, 15 Nov 2019 12:15:00 -0500 Received: by mail-oi1-f196.google.com with SMTP id v138so9241302oif.6 for ; Fri, 15 Nov 2019 09:15:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=OMJenj5JQASv6g4NovikQm2+Hb7lZX8x9WL40qMINts=; b=CBFLAcP+oKm5ozaC/dYCuIf8klMNXsh2hapTlsQCl2wIwMP890KgmIt8FubWjOJotW SBA0qHxfNEqf/6i9Jdz5242Bv3Qp2u6lAlduKS5V0Fuvapxf0kOztkzl27w0zsBtb8xX yTnmYMeItCp35Kq3H5eBWsRbw8ofmOm+ZBpYyFF12krdl0qWEAfg8Hcg7hzPswVqn1fN FwFNQRyyE3KBIFlaWKzS0W2mmgQ/hbL0TF60KX4gWFSxibKz0QDKtLPtOI4IrWzykGA8 7M2/Jp9d2h2Msqwj3bx5oQAdQZXvkYzLAGBZzJqyqk7VWIo6D482M+7RzUU3qO9b2Uly Fyqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=OMJenj5JQASv6g4NovikQm2+Hb7lZX8x9WL40qMINts=; b=Bu/xG3LTgOPpqqhovdlPtwjJf5On759b/q++kD1lSI7RVNOgwf/Q3kYfzZcV5iMY1c sUxvle8muKDZ2DO3vYaNgkxQOTj072pYvnTmjhUYw6bwMssynKSwqqUjdY2W6eUOzB8M d2vzS2AoeQyXkDiOhK4QRHxTKRwksdLyJBkmbocMFbRUhnhHlJly3o1TmklUYLezj4Rb VIyqdJpTFwoWfPCrKDJstLGq7LoWagt6JVDU2R3Y0dJ/6H9M2bDLcMa5iIbddyTzL5xX svSO7+9bktclm0B8QZAgGEbHv/gk6MJfqynF59w6Y6bxpSfcfH/pT0+T+Tj2WDDzTqA+ ioTQ== X-Gm-Message-State: APjAAAUUlnVVadZEV7/7WRVquUCNr1WJ8tXpQnOqDQljtZbIqeCEM/UE QZc3c37Tq9sQW+tcHvEGPEOIcPhepU/FV4qNGMOgTw== X-Google-Smtp-Source: APXvYqxHWXVF03C+YdxtSxrgLxdL91oUGsi161YRDrFwzpCwmUgbv+aRRG2bYG5Q9dZzAnZnGy6OsSdj2lBrotybY3s= X-Received: by 2002:aca:4ec6:: with SMTP id c189mr8959788oib.70.1573838099466; Fri, 15 Nov 2019 09:14:59 -0800 (PST) MIME-Version: 1.0 References: <20191114180303.66955-1-elver@google.com> <20191114195046.GP2865@paulmck-ThinkPad-P72> <20191114213303.GA237245@google.com> <20191114221559.GS2865@paulmck-ThinkPad-P72> <20191115164159.GU2865@paulmck-ThinkPad-P72> In-Reply-To: <20191115164159.GU2865@paulmck-ThinkPad-P72> From: Marco Elver Date: Fri, 15 Nov 2019 18:14:46 +0100 Message-ID: Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) To: "Paul E. McKenney" Cc: LKMM Maintainers -- Akira Yokosawa , Alan Stern , Alexander Potapenko , Andrea Parri , Andrey Konovalov , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Boqun Feng , Borislav Petkov , Daniel Axtens , Daniel Lustig , Dave Hansen , David Howells , Dmitry Vyukov , "H. Peter Anvin" , Ingo Molnar , Jade Alglave , Joel Fernandes , Jonathan Corbet , Josh Poimboeuf , Luc Maranget , Mark Rutland , Nicholas Piggin , Peter Zijlstra , Thomas Gleixner , Will Deacon , Eric Dumazet , kasan-dev , linux-arch , "open list:DOCUMENTATION" , linux-efi@vger.kernel.org, Linux Kbuild mailing list , LKML , Linux Memory Management List , "the arch/x86 maintainers" 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 On Fri, 15 Nov 2019 at 17:42, Paul E. McKenney wrote: > > On Fri, Nov 15, 2019 at 01:02:08PM +0100, Marco Elver wrote: > > On Thu, 14 Nov 2019 at 23:16, Paul E. McKenney wrote: > > > > > > On Thu, Nov 14, 2019 at 10:33:03PM +0100, Marco Elver wrote: > > > > On Thu, 14 Nov 2019, Paul E. McKenney wrote: > > > > > > > > > On Thu, Nov 14, 2019 at 07:02:53PM +0100, Marco Elver wrote: > > > > > > This is the patch-series for the Kernel Concurrency Sanitizer (KCSAN). > > > > > > KCSAN is a sampling watchpoint-based *data race detector*. More details > > > > > > are included in **Documentation/dev-tools/kcsan.rst**. This patch-series > > > > > > only enables KCSAN for x86, but we expect adding support for other > > > > > > architectures is relatively straightforward (we are aware of > > > > > > experimental ARM64 and POWER support). > > > > > > > > > > > > To gather early feedback, we announced KCSAN back in September, and have > > > > > > integrated the feedback where possible: > > > > > > http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@mail.gmail.com > > > > > > > > > > > > The current list of known upstream fixes for data races found by KCSAN > > > > > > can be found here: > > > > > > https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan > > > > > > > > > > > > We want to point out and acknowledge the work surrounding the LKMM, > > > > > > including several articles that motivate why data races are dangerous > > > > > > [1, 2], justifying a data race detector such as KCSAN. > > > > > > > > > > > > [1] https://lwn.net/Articles/793253/ > > > > > > [2] https://lwn.net/Articles/799218/ > > > > > > > > > > I queued this and ran a quick rcutorture on it, which completed > > > > > successfully with quite a few reports. > > > > > > > > Great. Many thanks for queuing this in -rcu. And regarding merge window > > > > you mentioned, we're fine with your assumption to targeting the next > > > > (v5.6) merge window. > > > > > > > > I've just had a look at linux-next to check what a future rebase > > > > requires: > > > > > > > > - There is a change in lib/Kconfig.debug and moving KCSAN to the > > > > "Generic Kernel Debugging Instruments" section seems appropriate. > > > > - bitops-instrumented.h was removed and split into 3 files, and needs > > > > re-inserting the instrumentation into the right places. > > > > > > > > Otherwise there are no issues. Let me know what you recommend. > > > > > > Sounds good! > > > > > > I will be rebasing onto v5.5-rc1 shortly after it comes out. My usual > > > approach is to fix any conflicts during that rebasing operation. > > > Does that make sense, or would you prefer to send me a rebased stack at > > > that point? Either way is fine for me. > > > > That's fine with me, thanks! To avoid too much additional churn on > > your end, I just replied to the bitops patch with a version that will > > apply with the change to bitops-instrumented infrastructure. > > My first thought was to replace 8/10 of the previous version of your > patch in -rcu (047ca266cfab "asm-generic, kcsan: Add KCSAN instrumentation > for bitops"), but this does not apply. So I am guessing that I instead > do this substitution when a rebase onto -rc1.. > > Except... > > > Also considering the merge window, we had a discussion and there are > > some arguments for targeting the v5.5 merge window: > > - we'd unblock ARM and POWER ports; > > - we'd unblock people wanting to use the data_race macro; > > - we'd unblock syzbot just tracking upstream; > > Unless there are strong reasons to not target v5.5, I leave it to you > > if you think it's appropriate. > > My normal process is to send the pull request shortly after -rc5 comes > out, but you do call out some benefits of getting it in sooner, so... > > What I will do is to rebase your series onto (say) -rc7, test it, and > see about an RFC pull request. > > One possible complication is the new 8/10 patch. But maybe it will > apply against -rc7? > > Another possible complication is this: > > scripts/kconfig/conf --syncconfig Kconfig > * > * Restart config... > * > * > * KCSAN: watchpoint-based dynamic data race detector > * > KCSAN: watchpoint-based dynamic data race detector (KCSAN) [N/y/?] (NEW) > > Might be OK in this case because it is quite obvious what it is doing. > (Avoiding pain from this is the reason that CONFIG_RCU_EXPERT exists.) > > But I will just mention this in the pull request. > > If there is a -rc8, there is of course a higher probability of making it > into the next merge window. > > Fair enough? Totally fine with that, sounds like a good plan, thanks! If it helps, in theory we can also drop and delay the bitops instrumentation patch until the new bitops instrumentation infrastructure is in 5.5-rc1. There won't be any false positives if this is missing, we might just miss a few data races until we have it. Thanks, -- Marco From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marco Elver Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) Date: Fri, 15 Nov 2019 18:14:46 +0100 Message-ID: References: <20191114180303.66955-1-elver@google.com> <20191114195046.GP2865@paulmck-ThinkPad-P72> <20191114213303.GA237245@google.com> <20191114221559.GS2865@paulmck-ThinkPad-P72> <20191115164159.GU2865@paulmck-ThinkPad-P72> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20191115164159.GU2865@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org To: "Paul E. McKenney" Cc: LKMM Maintainers -- Akira Yokosawa , Alan Stern , Alexander Potapenko , Andrea Parri , Andrey Konovalov , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Boqun Feng , Borislav Petkov , Daniel Axtens , Daniel Lustig , Dave Hansen , David Howells , Dmitry Vyukov , "H. Peter Anvin" , Ingo Molnar , Jade Alglave , Joel Fernandes , Jonathan Corbet List-Id: linux-arch.vger.kernel.org On Fri, 15 Nov 2019 at 17:42, Paul E. McKenney wrote: > > On Fri, Nov 15, 2019 at 01:02:08PM +0100, Marco Elver wrote: > > On Thu, 14 Nov 2019 at 23:16, Paul E. McKenney wrote: > > > > > > On Thu, Nov 14, 2019 at 10:33:03PM +0100, Marco Elver wrote: > > > > On Thu, 14 Nov 2019, Paul E. McKenney wrote: > > > > > > > > > On Thu, Nov 14, 2019 at 07:02:53PM +0100, Marco Elver wrote: > > > > > > This is the patch-series for the Kernel Concurrency Sanitizer (KCSAN). > > > > > > KCSAN is a sampling watchpoint-based *data race detector*. More details > > > > > > are included in **Documentation/dev-tools/kcsan.rst**. This patch-series > > > > > > only enables KCSAN for x86, but we expect adding support for other > > > > > > architectures is relatively straightforward (we are aware of > > > > > > experimental ARM64 and POWER support). > > > > > > > > > > > > To gather early feedback, we announced KCSAN back in September, and have > > > > > > integrated the feedback where possible: > > > > > > http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@mail.gmail.com > > > > > > > > > > > > The current list of known upstream fixes for data races found by KCSAN > > > > > > can be found here: > > > > > > https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan > > > > > > > > > > > > We want to point out and acknowledge the work surrounding the LKMM, > > > > > > including several articles that motivate why data races are dangerous > > > > > > [1, 2], justifying a data race detector such as KCSAN. > > > > > > > > > > > > [1] https://lwn.net/Articles/793253/ > > > > > > [2] https://lwn.net/Articles/799218/ > > > > > > > > > > I queued this and ran a quick rcutorture on it, which completed > > > > > successfully with quite a few reports. > > > > > > > > Great. Many thanks for queuing this in -rcu. And regarding merge window > > > > you mentioned, we're fine with your assumption to targeting the next > > > > (v5.6) merge window. > > > > > > > > I've just had a look at linux-next to check what a future rebase > > > > requires: > > > > > > > > - There is a change in lib/Kconfig.debug and moving KCSAN to the > > > > "Generic Kernel Debugging Instruments" section seems appropriate. > > > > - bitops-instrumented.h was removed and split into 3 files, and needs > > > > re-inserting the instrumentation into the right places. > > > > > > > > Otherwise there are no issues. Let me know what you recommend. > > > > > > Sounds good! > > > > > > I will be rebasing onto v5.5-rc1 shortly after it comes out. My usual > > > approach is to fix any conflicts during that rebasing operation. > > > Does that make sense, or would you prefer to send me a rebased stack at > > > that point? Either way is fine for me. > > > > That's fine with me, thanks! To avoid too much additional churn on > > your end, I just replied to the bitops patch with a version that will > > apply with the change to bitops-instrumented infrastructure. > > My first thought was to replace 8/10 of the previous version of your > patch in -rcu (047ca266cfab "asm-generic, kcsan: Add KCSAN instrumentation > for bitops"), but this does not apply. So I am guessing that I instead > do this substitution when a rebase onto -rc1.. > > Except... > > > Also considering the merge window, we had a discussion and there are > > some arguments for targeting the v5.5 merge window: > > - we'd unblock ARM and POWER ports; > > - we'd unblock people wanting to use the data_race macro; > > - we'd unblock syzbot just tracking upstream; > > Unless there are strong reasons to not target v5.5, I leave it to you > > if you think it's appropriate. > > My normal process is to send the pull request shortly after -rc5 comes > out, but you do call out some benefits of getting it in sooner, so... > > What I will do is to rebase your series onto (say) -rc7, test it, and > see about an RFC pull request. > > One possible complication is the new 8/10 patch. But maybe it will > apply against -rc7? > > Another possible complication is this: > > scripts/kconfig/conf --syncconfig Kconfig > * > * Restart config... > * > * > * KCSAN: watchpoint-based dynamic data race detector > * > KCSAN: watchpoint-based dynamic data race detector (KCSAN) [N/y/?] (NEW) > > Might be OK in this case because it is quite obvious what it is doing. > (Avoiding pain from this is the reason that CONFIG_RCU_EXPERT exists.) > > But I will just mention this in the pull request. > > If there is a -rc8, there is of course a higher probability of making it > into the next merge window. > > Fair enough? Totally fine with that, sounds like a good plan, thanks! If it helps, in theory we can also drop and delay the bitops instrumentation patch until the new bitops instrumentation infrastructure is in 5.5-rc1. There won't be any false positives if this is missing, we might just miss a few data races until we have it. Thanks, -- Marco 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=-13.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 322BFC43141 for ; Fri, 15 Nov 2019 17:15:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C4F6D2072A for ; Fri, 15 Nov 2019 17:15:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CBFLAcP+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4F6D2072A Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 356226B0005; Fri, 15 Nov 2019 12:15:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2E1B16B0006; Fri, 15 Nov 2019 12:15:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 108896B0007; Fri, 15 Nov 2019 12:15:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0236.hostedemail.com [216.40.44.236]) by kanga.kvack.org (Postfix) with ESMTP id EF5E16B0005 for ; Fri, 15 Nov 2019 12:15:01 -0500 (EST) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id A23385847 for ; Fri, 15 Nov 2019 17:15:01 +0000 (UTC) X-FDA: 76159162002.29.road64_eb10adc99e4c X-HE-Tag: road64_eb10adc99e4c X-Filterd-Recvd-Size: 9281 Received: from mail-oi1-f196.google.com (mail-oi1-f196.google.com [209.85.167.196]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Fri, 15 Nov 2019 17:15:00 +0000 (UTC) Received: by mail-oi1-f196.google.com with SMTP id x4so1286241oie.9 for ; Fri, 15 Nov 2019 09:15:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=OMJenj5JQASv6g4NovikQm2+Hb7lZX8x9WL40qMINts=; b=CBFLAcP+oKm5ozaC/dYCuIf8klMNXsh2hapTlsQCl2wIwMP890KgmIt8FubWjOJotW SBA0qHxfNEqf/6i9Jdz5242Bv3Qp2u6lAlduKS5V0Fuvapxf0kOztkzl27w0zsBtb8xX yTnmYMeItCp35Kq3H5eBWsRbw8ofmOm+ZBpYyFF12krdl0qWEAfg8Hcg7hzPswVqn1fN FwFNQRyyE3KBIFlaWKzS0W2mmgQ/hbL0TF60KX4gWFSxibKz0QDKtLPtOI4IrWzykGA8 7M2/Jp9d2h2Msqwj3bx5oQAdQZXvkYzLAGBZzJqyqk7VWIo6D482M+7RzUU3qO9b2Uly Fyqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=OMJenj5JQASv6g4NovikQm2+Hb7lZX8x9WL40qMINts=; b=sGtCGoB7mEDHA0gMNHDLJcV8gU+IWT3phm1Y/dxnuBwEo0iFXOJYhlzqtrv7m/Jd+N m9MLohEq7hbnpCjf2ZPe/bDM06bmDOohDYQwJaFx67RzXCpujz/9sWL32zYJcIj3Xws2 UfN82rU3eUnpS2iey9j6jL8x+4l5+btR78j15zHVs+Q5isRK4gPZIBE5mK5IaH7wTmaB Pa7LQJO2hMMDv1rek3gMfotqDdwCEt8j2Qcpfz5gqRHikEnvg37kxqYzq09YfNu2xMr4 ZKdFR1scwCnCykAgvVF5lrs4NgEJrE1362VSuVlD0FqinXrWvEB1BZ9205QgWcXmGAtH L1xg== X-Gm-Message-State: APjAAAUmFlBEuIUI3n0DfP5jOci7v1aaGVcw94O8+VPBNfffF2cvX9lb fZxKDYi5FbTcDQ4Sx7ByK+V5WID48AdzWnQHexemSA== X-Google-Smtp-Source: APXvYqxHWXVF03C+YdxtSxrgLxdL91oUGsi161YRDrFwzpCwmUgbv+aRRG2bYG5Q9dZzAnZnGy6OsSdj2lBrotybY3s= X-Received: by 2002:aca:4ec6:: with SMTP id c189mr8959788oib.70.1573838099466; Fri, 15 Nov 2019 09:14:59 -0800 (PST) MIME-Version: 1.0 References: <20191114180303.66955-1-elver@google.com> <20191114195046.GP2865@paulmck-ThinkPad-P72> <20191114213303.GA237245@google.com> <20191114221559.GS2865@paulmck-ThinkPad-P72> <20191115164159.GU2865@paulmck-ThinkPad-P72> In-Reply-To: <20191115164159.GU2865@paulmck-ThinkPad-P72> From: Marco Elver Date: Fri, 15 Nov 2019 18:14:46 +0100 Message-ID: Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) To: "Paul E. McKenney" Cc: LKMM Maintainers -- Akira Yokosawa , Alan Stern , Alexander Potapenko , Andrea Parri , Andrey Konovalov , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Boqun Feng , Borislav Petkov , Daniel Axtens , Daniel Lustig , Dave Hansen , David Howells , Dmitry Vyukov , "H. Peter Anvin" , Ingo Molnar , Jade Alglave , Joel Fernandes , Jonathan Corbet , Josh Poimboeuf , Luc Maranget , Mark Rutland , Nicholas Piggin , Peter Zijlstra , Thomas Gleixner , Will Deacon , Eric Dumazet , kasan-dev , linux-arch , "open list:DOCUMENTATION" , linux-efi@vger.kernel.org, Linux Kbuild mailing list , LKML , Linux Memory Management List , "the arch/x86 maintainers" Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 15 Nov 2019 at 17:42, Paul E. McKenney wrote: > > On Fri, Nov 15, 2019 at 01:02:08PM +0100, Marco Elver wrote: > > On Thu, 14 Nov 2019 at 23:16, Paul E. McKenney wrote: > > > > > > On Thu, Nov 14, 2019 at 10:33:03PM +0100, Marco Elver wrote: > > > > On Thu, 14 Nov 2019, Paul E. McKenney wrote: > > > > > > > > > On Thu, Nov 14, 2019 at 07:02:53PM +0100, Marco Elver wrote: > > > > > > This is the patch-series for the Kernel Concurrency Sanitizer (KCSAN). > > > > > > KCSAN is a sampling watchpoint-based *data race detector*. More details > > > > > > are included in **Documentation/dev-tools/kcsan.rst**. This patch-series > > > > > > only enables KCSAN for x86, but we expect adding support for other > > > > > > architectures is relatively straightforward (we are aware of > > > > > > experimental ARM64 and POWER support). > > > > > > > > > > > > To gather early feedback, we announced KCSAN back in September, and have > > > > > > integrated the feedback where possible: > > > > > > http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@mail.gmail.com > > > > > > > > > > > > The current list of known upstream fixes for data races found by KCSAN > > > > > > can be found here: > > > > > > https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan > > > > > > > > > > > > We want to point out and acknowledge the work surrounding the LKMM, > > > > > > including several articles that motivate why data races are dangerous > > > > > > [1, 2], justifying a data race detector such as KCSAN. > > > > > > > > > > > > [1] https://lwn.net/Articles/793253/ > > > > > > [2] https://lwn.net/Articles/799218/ > > > > > > > > > > I queued this and ran a quick rcutorture on it, which completed > > > > > successfully with quite a few reports. > > > > > > > > Great. Many thanks for queuing this in -rcu. And regarding merge window > > > > you mentioned, we're fine with your assumption to targeting the next > > > > (v5.6) merge window. > > > > > > > > I've just had a look at linux-next to check what a future rebase > > > > requires: > > > > > > > > - There is a change in lib/Kconfig.debug and moving KCSAN to the > > > > "Generic Kernel Debugging Instruments" section seems appropriate. > > > > - bitops-instrumented.h was removed and split into 3 files, and needs > > > > re-inserting the instrumentation into the right places. > > > > > > > > Otherwise there are no issues. Let me know what you recommend. > > > > > > Sounds good! > > > > > > I will be rebasing onto v5.5-rc1 shortly after it comes out. My usual > > > approach is to fix any conflicts during that rebasing operation. > > > Does that make sense, or would you prefer to send me a rebased stack at > > > that point? Either way is fine for me. > > > > That's fine with me, thanks! To avoid too much additional churn on > > your end, I just replied to the bitops patch with a version that will > > apply with the change to bitops-instrumented infrastructure. > > My first thought was to replace 8/10 of the previous version of your > patch in -rcu (047ca266cfab "asm-generic, kcsan: Add KCSAN instrumentation > for bitops"), but this does not apply. So I am guessing that I instead > do this substitution when a rebase onto -rc1.. > > Except... > > > Also considering the merge window, we had a discussion and there are > > some arguments for targeting the v5.5 merge window: > > - we'd unblock ARM and POWER ports; > > - we'd unblock people wanting to use the data_race macro; > > - we'd unblock syzbot just tracking upstream; > > Unless there are strong reasons to not target v5.5, I leave it to you > > if you think it's appropriate. > > My normal process is to send the pull request shortly after -rc5 comes > out, but you do call out some benefits of getting it in sooner, so... > > What I will do is to rebase your series onto (say) -rc7, test it, and > see about an RFC pull request. > > One possible complication is the new 8/10 patch. But maybe it will > apply against -rc7? > > Another possible complication is this: > > scripts/kconfig/conf --syncconfig Kconfig > * > * Restart config... > * > * > * KCSAN: watchpoint-based dynamic data race detector > * > KCSAN: watchpoint-based dynamic data race detector (KCSAN) [N/y/?] (NEW) > > Might be OK in this case because it is quite obvious what it is doing. > (Avoiding pain from this is the reason that CONFIG_RCU_EXPERT exists.) > > But I will just mention this in the pull request. > > If there is a -rc8, there is of course a higher probability of making it > into the next merge window. > > Fair enough? Totally fine with that, sounds like a good plan, thanks! If it helps, in theory we can also drop and delay the bitops instrumentation patch until the new bitops instrumentation infrastructure is in 5.5-rc1. There won't be any false positives if this is missing, we might just miss a few data races until we have it. Thanks, -- Marco