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=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 88E59C43331 for ; Mon, 30 Mar 2020 11:58:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63EF2206F6 for ; Mon, 30 Mar 2020 11:58:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729864AbgC3L61 (ORCPT ); Mon, 30 Mar 2020 07:58:27 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:51205 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729785AbgC3L61 (ORCPT ); Mon, 30 Mar 2020 07:58:27 -0400 Received: from fsav102.sakura.ne.jp (fsav102.sakura.ne.jp [27.133.134.229]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 02UBw4tU096873; Mon, 30 Mar 2020 20:58:04 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav102.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav102.sakura.ne.jp); Mon, 30 Mar 2020 20:58:04 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav102.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 02UBvw1n096795 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 30 Mar 2020 20:58:04 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH V3] kernel/hung_task.c: Introduce sysctl to print all traces when a hung task is detected To: Dmitry Vyukov Cc: Guilherme Piccoli , LKML , syzkaller , kernelci@groups.io, CKI Project , kbuild test robot , workflows@vger.kernel.org References: <20200327223646.20779-1-gpiccoli@canonical.com> <7fe65aef-94e1-b51a-0434-b1fe9d402d7b@i-love.sakura.ne.jp> From: Tetsuo Handa Message-ID: Date: Mon, 30 Mar 2020 20:57:56 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: workflows-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: workflows@vger.kernel.org On 2020/03/30 18:01, Dmitry Vyukov wrote: > On Mon, Mar 30, 2020 at 10:49 AM Dmitry Vyukov wrote: >> >> On Mon, Mar 30, 2020 at 2:43 AM Guilherme Piccoli >> wrote: >>> >>> Hi Tetsuo and Dmitry, thanks for noticing this Tetsuo. And sorry for >>> not looping you in the patch Dmitry, I wasn't aware that you were >>> working with testing. By the way, I suggest people interested in linux >>> testing to create a ML; I'd be glad to have looped such list, but I >>> couldn't find information about a group dealing with testing. >>> >>> So Tetsuo, you got it right: just change it to >>> "sysctl.kernel.hung_task_all_cpu_backtrace=1" and that should work >>> fine, once Vlastimil's patch gets merged (and I hope it happens soon). >>> Cheers, >>> >>> >>> Guilherme >> >> +LKML, workflows, syzkaller, kernelci, cki, kbuild >> >> Tetsuo, thanks for notifying again. >> >> Yes, kernel devs breaking all testing happens from time to time and >> currently there is no good way to address this. >> Other things I remember is the introduction of CONFIG_DEBUG_MEMORY, >> which defaults to =n and disables KASAN, which in turn produced an >> explosion of assorted crashes caused by memory corruptions; also >> periodic changes in kernel crash messages which I assume all testing >> systems parse and need to understand. >> >> Is there already a mailing list for this? Or should we create one? >> I.e. announce and changes that may need actions from all testing >> systems. I think we can create one. >> Another thing that may benefit from announcements is addition of new >> useful debugging configs. Currently they are introduced silently and >> don't reach the target audience. > > I've fixed this up: > https://github.com/google/syzkaller/commit/c8d1cc20df5ca5d9ea437054720fa3cfdfa1f578 Excuse me, but that commit is incorrect. There will be no /proc/sys/sysctl/kernel/hung_task_all_cpu_backtrace file. What Vlastimil's patch will allow is to set sysctl values via kernel command line option using "sysctl." as a prefix. That is, -hung_task_all_cpu_backtrace=1 +sysctl.kernel.hung_task_all_cpu_backtrace=1 on dashboard/config/*.cmdline files is what you need. > > But what would be even better is some kind of canned configs/settings > for testing systems so that I enable it once and then such changes > magically auto-happen for me. Yes, updating kernel config is a burden for kernel testing projects. I'm waiting for comments from more kernel testing projects on https://lkml.kernel.org/r/55c906c8-ca70-9d1b-a90f-49660773856b@i-love.sakura.ne.jp . > Imposing work on N testing systems maintainers is not good. > And there really is no good point in the current kernel dev process > for this. Announcing unmerged changes is too early (as this patch > showed). And once it's in linux-next it's already too late.. > And I don't want to be inventing a new unique kernel configuration for > testing. I don't think it's the right way to approach this. Whatever > is "the testing configuration", whatever kernel developers want to see > in task hang reports, I just want the system to provide that. >