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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 ABFDCCA90AF for ; Wed, 13 May 2020 11:25:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9362020753 for ; Wed, 13 May 2020 11:25:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728258AbgEMLZF (ORCPT ); Wed, 13 May 2020 07:25:05 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:57550 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726020AbgEMLZD (ORCPT ); Wed, 13 May 2020 07:25:03 -0400 Received: from fsav105.sakura.ne.jp (fsav105.sakura.ne.jp [27.133.134.232]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 04DBOOjo033442; Wed, 13 May 2020 20:24:24 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav105.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav105.sakura.ne.jp); Wed, 13 May 2020 20:24:24 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav105.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 04DBOOjV033412 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 13 May 2020 20:24:24 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] printk: Add loglevel for "do not print to consoles". To: Michal Hocko , Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , linux-kernel@vger.kernel.org, Dmitry Safonov , Yafang Shao References: <4dae86af-1d9a-f5a8-cff6-aa91ec038a79@i-love.sakura.ne.jp> <20200428121828.GP28637@dhcp22.suse.cz> <20200428154532.GU28637@dhcp22.suse.cz> <20200429142106.GG28637@dhcp22.suse.cz> <20200513062652.GM413@jagdpanzerIV.localdomain> <20200513100413.GH17734@linux-b0ei> <20200513104938.GW29153@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: Date: Wed, 13 May 2020 20:24:24 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200513104938.GW29153@dhcp22.suse.cz> 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 On 2020/05/13 19:49, Michal Hocko wrote: > On Wed 13-05-20 12:04:13, Petr Mladek wrote: >> What is so special about OOM dump task so that it would deserve such >> complications? > > Nothing really. Except for the potential amount of the output. "echo t > /proc/sysrq-trigger" from userspace program is another example. > But as > you've said there are two ways around that. Disable this output if you > do not need it or make it a lower loglevel. Disable this output for syslog is not acceptable for me, but disable this output for consoles is preferable for me. > I simply cannot tell whether somebody considers > dump_tasks an important information to be printed on consoles. I don't think dump_tasks() is important information to be printed on consoles. But since somebody might think dump_tasks() is important information to be printed on consoles, I suggest switching KERN_NO_CONSOLES using e.g. sysctl. > > If there is any need to control which messages should be routed to which > backend then the proper solution would be to filter messages per log > level per backend. Possible backends will be "zero or more than zero" consoles + "zero or one" syslog, and KERN_NO_CONSOLES is a method for force selecting "zero" console backend. > But I have no idea how feasible this is for the > existing infrastructure - or maybe it already exists... There is per-console loglevel proposal (which allows selecting "some" console backends). But it is based on KERN_$LOGLEVEL which is too rough-grained.