From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751250AbdGOFFq (ORCPT ); Sat, 15 Jul 2017 01:05:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52188 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751019AbdGOFFo (ORCPT ); Sat, 15 Jul 2017 01:05:44 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com E48BD368E6 Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=fdinitto@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com E48BD368E6 Subject: Re: [PATCH 0/2] Avoid crashes by early (boot) consoles using init memory To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Andrew Morton , Peter Zijlstra , Matt Redfearn , Greg Kroah-Hartman , Jiri Slaby , "David S. Miller" , Alan Cox , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky References: <1500036673-7122-1-git-send-email-pmladek@suse.com> <956ce40c-1640-387a-0ec9-9045c7d8af4b@redhat.com> <20170714143751.GB32632@pathway.suse.cz> From: "Fabio M. Di Nitto" Message-ID: Date: Sat, 15 Jul 2017 07:05:35 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170714143751.GB32632@pathway.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Sat, 15 Jul 2017 05:05:44 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/14/2017 4:37 PM, Petr Mladek wrote: > On Fri 2017-07-14 14:57:45, Fabio M. Di Nitto wrote: >> Hi Petr, >> >> On 7/14/2017 2:51 PM, Petr Mladek wrote: >>> Some early consoles have code and data in the init section. It makes some >>> sense but this might cause problems when they are not replaced by >>> the real console in time. The two patches fix the safequard and >>> help to avoid the problems. >>> >>> I though about removing keep_bootcon option completely. But it is useful >>> at least for now. >> >> Let´s just keep in mind that keep_bootcon was introduced only to debug >> issues (read crashes or hangs) that could happen between disabling >> bootconsole and enabling the real console. It shouldn´t be used for >> anything else really. > > This was my initial replay as well. But then I realized that > it was a bad idea to use a freed code and data to debug any other > issue. It would just create crazy issues on its own. Perhaps some changes that were made later in the code introduced this behavior. I honestly didn´t check. It´s been just so long ago :-) > > I tried to google 'keep_bootcon'. It found several links to strange > crashes related to this option. Maybe I was not patient enough but > I did not find any page where this option was suggested and helped. It´s in Documentation/admin-guide/kernel-parameters.txt. It´s also rare that consoles are not working or something is crashing in that small window, so I am not entirely surprised that there are few to none references of users using it. > > I still think that the option makes some sense but only when > it does not cause more breakages on its own. agreed. Cheers Fabio > >> If the new code can replace keep_bootcon, by all mean, go for it :-) > > keep_bootcon stays usable for most early consoles. We print a warning > when an unusable console is disabled too early. Also there is a > comment how to fix it. > > Best Regards, > Petr >