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=-6.3 required=3.0 tests=BAYES_00, BUG6152_INVALID_DATE_TZ_ABSURD,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,INVALID_DATE_TZ_ABSURD, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CA536C388F7 for ; Thu, 22 Oct 2020 14:53:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 653642463B for ; Thu, 22 Oct 2020 14:53:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="GKkfNcEV"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="KZ8nxtGR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S368283AbgJVOxT (ORCPT ); Thu, 22 Oct 2020 10:53:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S368275AbgJVOxR (ORCPT ); Thu, 22 Oct 2020 10:53:17 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54964C0613CE for ; Thu, 22 Oct 2020 07:53:17 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1603378395; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=O0H/03sI53oZZCAYw4B2lRGz8cXK5h4OEQ0DMNG/lhA=; b=GKkfNcEVprEweNcn+AN6OjYO0EpUqi59ggnM9SIPh+1CdeWZMo/556tPnun6HECXqzVXz4 RHtJgVCBFDMtCSz0+8gXTOldB8cQOrclDLA6grM3jh3Dt1gimzN3OTXQmpz56ViW9URqpe gcq9yLZgYvOFsN/5T9NZtlXX42Q7ILp87j85E3lCd+hJqeY5AJdIkb4b0DDaElY1xIeAGc u0evnKjYAzBwETrahlRUDTgF/2Y/B7rlRBx9gvYXSFQ1sjyXIUc+ew5WABbRaSqHfM+mjO 2TmmjRnM8u/wwkN8Dl8Ib4L+ywxdP9AAbvKS5/VE38rC09pga4f9pufX49joVQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1603378395; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=O0H/03sI53oZZCAYw4B2lRGz8cXK5h4OEQ0DMNG/lhA=; b=KZ8nxtGRqM+Qxs4tbXK2nONuM6YJ0B3NjFR2Ss1/Oe/k1CrOCik3UETmKSMrQJ0AZeroeT eJypfzFDcP9tJcAA== To: Guenter Roeck , Petr Mladek , Sergey Senozhatsky , Steven Rostedt Cc: Linus Torvalds , Shreyas Joshi , shreyasjoshi15@gmail.com, Greg Kroah-Hartman , Sergey Senozhatsky , linux-kernel@vger.kernel.org Subject: Re: [RFC 1/2] printk: Add kernel parameter: mute_console In-Reply-To: <5a30b3e8-c2c3-ceae-517e-c93fb2c3118f@roeck-us.net> References: <20201022114228.9098-1-pmladek@suse.com> <20201022114228.9098-2-pmladek@suse.com> <87a6wez9s4.fsf@jogness.linutronix.de> <5a30b3e8-c2c3-ceae-517e-c93fb2c3118f@roeck-us.net> Date: Thu, 22 Oct 2020 16:59:15 +0206 Message-ID: <877driz50k.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-10-22, Guenter Roeck wrote: >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >>> index 02d4adbf98d2..52b9e7f5468d 100644 >>> --- a/Documentation/admin-guide/kernel-parameters.txt >>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>> @@ -2974,6 +2974,12 @@ >>> Used for mtrr cleanup. It is spare mtrr entries number. >>> Set to 2 or more if your graphical card needs more. >>> >>> + mute_console [KNL] >>> + Completely disable printing of kernel messages to >>> + the console. It can still be used as stdin, stdout, > > "to all consoles" > >>> + and stderr for the init process. Also it can be used >>> + for login. >> >> IMHO it would make more sense for this to be a console option: >> >> console=ttyS0,115200,mute >> >> Then other consoles could still exist that are not muted. >> > Then why specify this console in the first place ? Because you may still want to use it for stdin/stdout/stderr of PID 1 and/or logins. I understood "mute" as meaning the user does not want to see kernel logging. But everything else should still work as usual. >> On a side note, I am considering proposing something similar for my >> printk-rework efforts. Once console printers are moved to kthreads, some >> users may not care about latencies and instead prefer synchronous >> printing. My idea for this is to provide a "sync" option for the >> console: >> >> console=ttyS0,115200,sync > > The whole point of the exercise is to disable all consoles, including > default ones which are not explicitly specified on the command line. In that case I think specifying something like: console=null makes that most sense. I think implementing a "null console" driver would be quite simple. Then there would be no need for special handling in the printk subsystem. John Ogness