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=-7.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 68360C43141 for ; Fri, 15 Nov 2019 16:42:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3931620801 for ; Fri, 15 Nov 2019 16:42:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573836124; bh=jkErE5GY/mWn/HAQI9cUc0wleSx4QKoShYxAgztG5XE=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=ieljwP1pauJDcaUrKoVy/krMgC+SqCWahBaYc8VlJEh4ixrOppkLmAgfv//z2OLcR yqKxU6D+eAHFRKgvRG9xBz/u+F/Ewn/jewCO1gLtVub/9Nq2Y1pjTH38/KIcaPGQXP h/Z+emjrCfljmjnllbqSN3zkW8vgRvx6h1RDkJss= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727695AbfKOQmD (ORCPT ); Fri, 15 Nov 2019 11:42:03 -0500 Received: from mail.kernel.org ([198.145.29.99]:54372 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727537AbfKOQmB (ORCPT ); Fri, 15 Nov 2019 11:42:01 -0500 Received: from paulmck-ThinkPad-P72.home (unknown [199.201.64.129]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9D54220718; Fri, 15 Nov 2019 16:42:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573836120; bh=jkErE5GY/mWn/HAQI9cUc0wleSx4QKoShYxAgztG5XE=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=jKeRzm1CqhWwhTOzvKLKTOqY8ZuNPidt2GWCVinFuuMMZXNeqrLAasv7MSXXprvyw WKFvnCPoHjdbqYUxA/5m6WhK2VCHyGzSwDCcp0dgUPpVa4AA66nzNeIhM3rpHnhr4+ SVw3qrsT+UW6bLbgxtLO6DLHoVJxo+hOSp8TOSHo= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id F1C0035207BD; Fri, 15 Nov 2019 08:41:59 -0800 (PST) Date: Fri, 15 Nov 2019 08:41:59 -0800 From: "Paul E. McKenney" To: Marco Elver 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 Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) Message-ID: <20191115164159.GU2865@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20191114180303.66955-1-elver@google.com> <20191114195046.GP2865@paulmck-ThinkPad-P72> <20191114213303.GA237245@google.com> <20191114221559.GS2865@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) Date: Fri, 15 Nov 2019 08:41:59 -0800 Message-ID: <20191115164159.GU2865@paulmck-ThinkPad-P72> References: <20191114180303.66955-1-elver@google.com> <20191114195046.GP2865@paulmck-ThinkPad-P72> <20191114213303.GA237245@google.com> <20191114221559.GS2865@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Marco Elver 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, 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? Thanx, Paul