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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 31103C282CE for ; Wed, 22 May 2019 12:40:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E66B21773 for ; Wed, 22 May 2019 12:40:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729364AbfEVMkf (ORCPT ); Wed, 22 May 2019 08:40:35 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:58277 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728438AbfEVMkf (ORCPT ); Wed, 22 May 2019 08:40:35 -0400 Received: from fsav301.sakura.ne.jp (fsav301.sakura.ne.jp [153.120.85.132]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x4MCct1g079574; Wed, 22 May 2019 21:38:55 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav301.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav301.sakura.ne.jp); Wed, 22 May 2019 21:38:55 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav301.sakura.ne.jp) Received: from [192.168.1.8] (softbank126012062002.bbtec.net [126.12.62.2]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x4MCclHk079384 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Wed, 22 May 2019 21:38:54 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] kernel/hung_task.c: Monitor killed tasks. From: Tetsuo Handa To: Stephen Rothwell Cc: Petr Mladek , Andrew Morton , Ingo Molnar , Peter Zijlstra , "Paul E. McKenney" , Vitaly Kuznetsov , Liu Chuansheng , Valdis Kletnieks , linux-kernel@vger.kernel.org, Dmitry Vyukov References: <1557745331-10367-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20190515105540.vyzh6n62rqi5imqv@pathway.suse.cz> <20190516115758.6v7oitg3vbkfhh5j@pathway.suse.cz> Message-ID: Date: Wed, 22 May 2019 21:38:45 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Stephen. I want to send debug printk() patches to linux-next.git. Petr Mladek is suggesting me to have a git tree for debug printk() patches. But it seems that there is "git quiltimport" command, and I prefer "subversion + quilt", and I don't have trees for sending "git pull" requests. Therefore, just ignoring "git quiltimport" failure is fine. What do you think? On 2019/05/16 21:38, Tetsuo Handa wrote: > On 2019/05/16 20:57, Petr Mladek wrote: >> CCed Stephen to discuss linux-next related question at the bottom >> of the mail. >> >> On Thu 2019-05-16 17:19:12, Tetsuo Handa wrote: >>> On 2019/05/15 19:55, Petr Mladek wrote: >>> But in the context of syzbot's testing where there are only 2 CPUs >>> in the target VM (which means that only small number of threads and >>> not so much memory) and threads get SIGKILL after 5 seconds from fork(), >>> being unable to reach do_exit() within 10 seconds is likely a sign of >>> something went wrong. For example, 6 out of 7 trials of a reproducer for >>> https://syzkaller.appspot.com/bug?id=835a0b9e75b14b55112661cbc61ca8b8f0edf767 >>> resulted in "no output from test machine" rather than "task hung". >>> This patch is revealing that such killed threads are failing to reach >>> do_exit() because they are trapped at unkillable retry loop due to a >>> race bug. >>> >>> Therefore, I would like to try this patch in linux-next.git for feasibility >>> testing whether this patch helps finding more bugs and reproducers for such >>> bugs, by bringing "unable to terminate threads" reports out of "no output from >>> test machine" reports. We can add sysctl settings before sending to linux.git. >> >> In this case, the watchdog should get enabled on with >> CONFIG_DEBUG_AID_FOR_SYZBOT > > Since "[PATCH] printk: Monitor change of console loglevel." is one time (only > needed until we find the reason of silence), testing on only linux-next.git > is sufficient and it gets enabled on with CONFIG_DEBUG_AID_FOR_SYZBOT. > >> >> Also we should ask/inform Stephen about this. I am not sure >> if he is willing to resolve eventual conflicts for these >> syzboot-specific patches that are not upstream candidates. >> >> A solution might be to create sysbot-specific for-next branch >> that Stephen might simply ignore when there are conflicts. >> And you would be responsible for updating it. > > syzbot tests not only linux-next.git but also various trees, and tests > attempted depends on target git tree. Therefore, apart from whether we > can introduce a kernel config option for fuzzing testing, > "[PATCH] kernel/hung_task.c: Monitor killed tasks." is expected to be > in linux.git. This patch will eventually become upstream candidate. >