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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8802AC433EF for ; Tue, 9 Nov 2021 16:19:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 670BB6103C for ; Tue, 9 Nov 2021 16:19:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234903AbhKIQV7 (ORCPT ); Tue, 9 Nov 2021 11:21:59 -0500 Received: from wnew4-smtp.messagingengine.com ([64.147.123.18]:40917 "EHLO wnew4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234118AbhKIQV7 (ORCPT ); Tue, 9 Nov 2021 11:21:59 -0500 Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailnew.west.internal (Postfix) with ESMTP id 9E64C2B011F4; Tue, 9 Nov 2021 11:19:11 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute5.internal (MEProxy); Tue, 09 Nov 2021 11:19:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kroah.com; h= date:from:to:cc:subject:message-id:references:mime-version :content-type:in-reply-to; s=fm2; bh=w6h/00s3fE/I2eJ4cKpEmxU04lj siJquGF6dd7lneQM=; b=FBMjAAKXuPFhilEYET/+Al0Gg7ZcnoAxLtAryS2Itsm PFnBEJpTtecEfHPvXBaqzHPDbKDlrdvxqgt/wbfwWizWwVYM9XB9jOOgg5PBOHpo zOfK2W9oHMOTuZuzEiKJhfP3EbajoX92yS0i5279Q6CUxZiynZH7AxdrTetCP9aL 2ytYCPcZNOuZHf8LxSDvZNdZ/ksEteLg9u5tKlu6ZeuslFiBxO8ICM/U7L6Uu7CM /lLpnSVQZdkogpxaDw9u80puLasJx+r/ES3DCSG2HPnyyg1BmsX6QIXhk+CuWPDd HqOtHjx6Zz7Zie/RaE9QgJWeHgYokXLDqNXFw/iyluw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm1; bh=w6h/00 s3fE/I2eJ4cKpEmxU04ljsiJquGF6dd7lneQM=; b=mpkPx3SFw0zVDkEJlXZwKO gDL5KhA4qdM7T7Xbt2/ZMPjYLuStFjY6PEMYt4EEeRhLfnkhM/+qHLBecJPzHsHt Wxwf27O+8B03nIL9WUQePMqMUdq8G+gwH0Y1zTJ2TTdnpVIiq7Bl54U1jn81USNV FgsgeYL5iSpY4est1xYc7T5rF/YMXKzFTB1416UCkHKMYqRzjnic6Zirtcu4Smti olVEIl7114DcQiIQR+B0+y9rAe3iysXdZlwx4vFyKjlIFedsSGsKbiH7PfqsV3BF h4ptFI+SqfGd3rVhE8RxmoyMPNkzMd3qTrWR950w/y+rPOfKsRn/EljmIprP8RYA == X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvuddrudeggdekiecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpeffhffvuffkfhggtggujgesthdtredttddtvdenucfhrhhomhepifhrvghgucfm jfcuoehgrhgvgheskhhrohgrhhdrtghomheqnecuggftrfgrthhtvghrnhephfegleetue eitdegiedutefhvdehtedtheejkeegkeejkeetkeefteevieffvdffnecuffhomhgrihhn pehkvghrnhgvlhdrohhrghdpshhpihhnihgtshdrnhgvthenucevlhhushhtvghrufhiii gvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpehgrhgvgheskhhrohgrhhdrtghomh X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 9 Nov 2021 11:19:10 -0500 (EST) Date: Tue, 9 Nov 2021 17:19:09 +0100 From: Greg KH To: Petr Mladek Cc: stable@vger.kernel.org, Greg Kroah-Hartman , Yi Fan , shreyas.joshi@biamp.com, Joshua Levasseur , sashal@kernel.org, Guenter Roeck , Sergey Senozhatsky Subject: Re: [PATCH] printk/console: Allow to disable console output by using console="" or console=null Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Nov 09, 2021 at 04:53:26PM +0100, 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 > Reviewed-by: Guenter Roeck > Tested-by: Guenter Roeck > Acked-by: Sergey Senozhatsky > Signed-off-by: Petr Mladek > Link: https://lore.kernel.org/r/20201111135450.11214-3-pmladek@suse.com > --- > > This is backport of the commit 3cffa06aeef7ece30f6b5ac0e > ("printk/console: Allow to disable console output by using > console="" or console=null") for stable release: > > + 4.4, 4.9, 4.14, 4.19, 5.4 > > Please, use the original upstream commit for stable release: > > + 5.10 > > It should fix the problem reported at > https://www.spinics.net/lists/stable/msg509616.html Thanks, now all queued up! greg k-h