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 12BE0C2BA1A for ; Sat, 25 Apr 2020 01:08:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E25A820776 for ; Sat, 25 Apr 2020 01:08:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726122AbgDYBIa (ORCPT ); Fri, 24 Apr 2020 21:08:30 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:57122 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726076AbgDYBI3 (ORCPT ); Fri, 24 Apr 2020 21:08:29 -0400 Received: from fsav104.sakura.ne.jp (fsav104.sakura.ne.jp [27.133.134.231]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 03P17mZV083687; Sat, 25 Apr 2020 10:07:48 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav104.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav104.sakura.ne.jp); Sat, 25 Apr 2020 10:07:48 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav104.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 03P17mu8083684 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 25 Apr 2020 10:07:48 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] printk: Add loglevel for "do not print to consoles". To: Sergey Senozhatsky Cc: Petr Mladek , Steven Rostedt , linux-kernel@vger.kernel.org, Dmitry Safonov , Michal Hocko , Yafang Shao References: <20200424024239.63607-1-penguin-kernel@I-love.SAKURA.ne.jp> <20200425004609.GE8982@jagdpanzerIV.localdomain> From: Tetsuo Handa Message-ID: <842ff40b-a232-6098-4333-996a3033b30a@i-love.sakura.ne.jp> Date: Sat, 25 Apr 2020 10:07:45 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200425004609.GE8982@jagdpanzerIV.localdomain> 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 2020/04/25 9:46, Sergey Senozhatsky wrote: > On (20/04/24 11:42), Tetsuo Handa wrote: > [..] >> @@ -19,6 +19,7 @@ static inline int printk_get_level(const char *buffer) >> switch (buffer[1]) { >> case '0' ... '7': >> case 'c': /* KERN_CONT */ >> + case 'S': /* KERN_NO_CONSOLES */ >> return buffer[1]; >> } >> } > > So this means NO_CONSOLES_AT_ALL, slow + fast ones. Right. > I wonder if this > wants to be NO_SLOW_CONSOLES instead. Which then brings us to the > next question - can this be done with per-console loglevel setting? It is difficult to define what is slow consoles. While netconsole will be a fast console, we can forward kernel messages via syslog daemon if desired. NO_SLOW_CONSOLES might be useful for immediate notification like panic(). But KERN_NO_CONSOLES is not for immediate notification like panic(). KERN_NO_CONSOLES is for type of messages where "saved for later analysis" is important but "printed for immediate notification" is not important. In other words, KERN_NO_CONSOLES is NOT for dying messages where "printed for immediate notification" is important.