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=-6.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 36DF1C388F9 for ; Thu, 12 Nov 2020 01:36:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0F52206F1 for ; Thu, 12 Nov 2020 01:36:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="geTCy/5I" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729057AbgKLBgu (ORCPT ); Wed, 11 Nov 2020 20:36:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37756 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728002AbgKKX7X (ORCPT ); Wed, 11 Nov 2020 18:59:23 -0500 Received: from mail-pg1-x541.google.com (mail-pg1-x541.google.com [IPv6:2607:f8b0:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A36D5C0613D4 for ; Wed, 11 Nov 2020 15:59:21 -0800 (PST) Received: by mail-pg1-x541.google.com with SMTP id f38so2608850pgm.2 for ; Wed, 11 Nov 2020 15:59:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=tsmfCCdrbb/ZwZwSPwH4J4qd2xy4d6TEFRqpFFfpq9c=; b=geTCy/5ITpdMoGYEJmczBceJppWgeubVn5xOGwIDmtN8SlmwgKCqB3PTAaK6VLxmc+ ZLONDAbcifEOKoezQPQhbZUlQ6gIAZbgG51ANfRAQZkKiSJLYSFBRZgLVvDwE2lW4JG/ PtTzihFmonMJjNqmT75o25IKPISNvW+7YiIMGAlb+sxRcJm4wFjR9gXKajYVqKHTZhHO 2VAJhVECVQRaZ5Kx8pzBredrCjkTz1+4UfnM8kTOWpV/AXoRuwKy6kANKfpxxJAP+Rav lDmmnMMPVh3b02vhvPZ7C3ws500Kbrv8O2qtGhp2eanuTWH8PB1k8s3g+MRuzt316ERN FU+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=tsmfCCdrbb/ZwZwSPwH4J4qd2xy4d6TEFRqpFFfpq9c=; b=egBOWYnETdan5BWU1pY7RBuiROERHOYXPDv+L4hSk6iprQNPk/7lx94v+3AnvZPxkV 9fHMIVpOQEXaHu2E5kM8btRZJBoBqIIgRk1uvyaXBA3dZjCGuUj1r/4/hEV7OQXM8bhN tmXtdFjVccfw9WdlUzjHN0PU8Y1wcQQmnNea6GxcqtHPf69dLeta7l/XTzTdfr7PLZpZ wJiSDu0nJ7QhGPtz0dfsJoBHXfzOQSIOK11ANULUxCuKx9NE0FnUbC2X2PgjQTnNUikl +ryAH8N4H5pyAInKN0jRZelelMkQZiJahrlHBzs+nc3RVn90ZQ6ZB87Qqh7Kb88Vjfjh QSEA== X-Gm-Message-State: AOAM532tgI25y4WmSsb/ScnW4dW7cvkcbBu/j39K77UGBUHpdfb+B8qc COWHARjZpvJXJkhVnBgFe68= X-Google-Smtp-Source: ABdhPJyThberwyLK0MBCHy4nDKzI34WJDTKxIMmxMQRgKRXs+t4v0XJ/A9ed6FRXDaefwkt4EzxHNw== X-Received: by 2002:a63:1357:: with SMTP id 23mr23511560pgt.13.1605139161110; Wed, 11 Nov 2020 15:59:21 -0800 (PST) Received: from localhost ([2409:10:2e40:5100:6e29:95ff:fe2d:8f34]) by smtp.gmail.com with ESMTPSA id n72sm4187988pfd.202.2020.11.11.15.59.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2020 15:59:20 -0800 (PST) Date: Thu, 12 Nov 2020 08:59:18 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , John Ogness , Linus Torvalds , Guenter Roeck , Shreyas Joshi , shreyasjoshi15@gmail.com, Greg Kroah-Hartman , Sergey Senozhatsky , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] printk/console: Allow to disable console output by using console="" or console=null Message-ID: References: <20201111135450.11214-1-pmladek@suse.com> <20201111135450.11214-3-pmladek@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201111135450.11214-3-pmladek@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/11/11 14:54), Petr Mladek wrote: > The commit 48021f98130880dd74 ("printk: handle blank console arguments > passed in.") prevented crash caused by empty console= parameter value. > > Unfortunately, this value is widely used on Chromebooks to disable > the console output. The above commit caused performance regression > because the messages were pushed on slow console even though nobody > was watching it. > > Use ttynull driver explicitly for console="" and console=null > parameters. It has been created for exactly this purpose. > > It causes that preferred_console is set. As a result, ttySX and ttyX > are not used as a fallback. And only ttynull console gets registered by > default. > > It still allows to register other consoles either by additional console= > parameters or SPCR. It prevents regression because it worked this way even > before. Also it is a sane semantic. Preventing output on all consoles > should be done another way, for example, by introducing mute_console > parameter. > > Link: https://lore.kernel.org/r/20201006025935.GA597@jagdpanzerIV.localdomain > Suggested-by: Sergey Senozhatsky > Signed-off-by: Petr Mladek Acked-by: Sergey Senozhatsky -ss