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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 7463CC2BD09 for ; Wed, 4 Dec 2019 12:22:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 38DA9207DD for ; Wed, 4 Dec 2019 12:22:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 38DA9207DD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A64296B0A81; Wed, 4 Dec 2019 07:22:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A15CB6B0A82; Wed, 4 Dec 2019 07:22:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 92BB56B0A83; Wed, 4 Dec 2019 07:22:20 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0240.hostedemail.com [216.40.44.240]) by kanga.kvack.org (Postfix) with ESMTP id 7CE526B0A81 for ; Wed, 4 Dec 2019 07:22:20 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 2D3F2180AD811 for ; Wed, 4 Dec 2019 12:22:20 +0000 (UTC) X-FDA: 76227371640.22.lunch52_14483c6396223 X-HE-Tag: lunch52_14483c6396223 X-Filterd-Recvd-Size: 5787 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Dec 2019 12:22:19 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4BBA7AE34; Wed, 4 Dec 2019 12:22:15 +0000 (UTC) Date: Wed, 4 Dec 2019 13:22:12 +0100 From: Petr Mladek To: Alexander Potapenko Cc: Steven Rostedt , Qian Cai , Marco Elver , Eric Biggers , Christoph Hellwig , Herbert Xu , Harry Wentland , Vegard Nossum , Dmitry Vyukov , Linux Memory Management List , Al Viro , Andreas Dilger , Andrew Morton , Andrey Konovalov , Andrey Ryabinin , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Christoph Hellwig , "Darrick J. Wong" , "David S. Miller" , Dmitry Torokhov , Eric Dumazet , Eric Van Hensbergen , Greg Kroah-Hartman , Ilya Leoshkevich , Ingo Molnar , Jason Wang , Jens Axboe , Marek Szyprowski , Mark Rutland , "Martin K. Petersen" , Martin Schwidefsky , Matthew Wilcox , "Michael S. Tsirkin" , Michal Simek , Randy Dunlap , Robin Murphy , Sergey Senozhatsky , Takashi Iwai , Theodore Ts'o , Thomas Gleixner , Vasily Gorbik , Wolfram Sang Subject: Re: [PATCH RFC v3 18/36] kmsan: disable LOCK_DEBUGGING_SUPPORT Message-ID: <20191204122212.ziwntau5hrokrpmk@pathway.suse.cz> References: <591B421C-F7AB-4394-83B5-AD3A86580C64@lca.pw> <20191203133815.05a020fc@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170912 (1.9.0) 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: Archived-At: List-Archive: List-Post: On Wed 2019-12-04 09:41:15, Alexander Potapenko wrote: > On Tue, Dec 3, 2019 at 7:38 PM Steven Rostedt wrote: > > > > On Tue, 3 Dec 2019 16:14:17 +0100 > > Alexander Potapenko wrote: > > > > > On Tue, Dec 3, 2019 at 4:00 PM Qian Cai wrote: > > > > > > > > > > > > > > > > > On Dec 3, 2019, at 9:35 AM, Alexander Potapenko wrote: > > > > > > > > > > At this point I don't really know why KMSAN and lockdep don't play > > > > > well together, but I'm not expecting anyone to use them together > > > > > either. > > > > > > > > Of course people will use those together. For example, distro debug kernel variants. > > > Some tools are just not designed to work together. > > > For example, you won't be able to compile the kernel with both KASAN > > > and KMSAN enabled at the same time. > > > > > > Lockdep doesn't require any instrumentation to work, so it _might_ be > > > possible to make it work with KMSAN, but it will probably still slow > > > down the things to an unacceptable level. > > > I'm inclining towards disabling the two together for now, unless > > > anyone is willing to address that issue. > > > > Note, I'm much more interested in someone running with lockdep than > > with KMSAN. Thus, you may not get as much use if you do not work with > > lockdep. I enable lockdep first when testing out my code. If KMSAN is > > not compatible, it wont get enabled. > > > > > > > > Please let me know if you think I need to keep the link to > > > https://github.com/google/kmsan/issues/57 in the Kconfig comment, > > > right now it looks like: > > > > > > # KMSAN is currently incompatible with lockdep. > > > > > > > Function tracing had lots of issues with lockdep, but I worked hard to > > make sure they could be compatible. This usually required having the > > lockdep code not be traced. Is it possible to have the same with KMSAN. > > That is, have KMSAN not look at anything that lockdep does? > > > > -- Steve > Qian, Steve, thanks for the data points. > I thought it might be more valuable to cut some edges to make KMSAN > available to early users, Makes sense to me. > but in the case most developers use a single > build for testing it indeed makes more sense to fix lockdep > interoperability. > I'll look into that. IMHO, a generic distro debug kernel could not enable debugging options that would significantly slow down the kernel. Most users would refuse using such kernels. Also they might slow down the system to the point that many problems won't be visible. For example, I do not see KASAN enabled in SUSE debug kernel. I guess that it will be the same with KMSAN. These options can be enabled in custom kernels when debugging particular problems. Best Regards, Petr