From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936488Ab3DRRom (ORCPT ); Thu, 18 Apr 2013 13:44:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56343 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936472Ab3DRRok (ORCPT ); Thu, 18 Apr 2013 13:44:40 -0400 Date: Thu, 18 Apr 2013 13:44:32 -0400 From: Don Zickus To: "Eric W. Biederman" Cc: linux-watchdog@vger.kernel.org, kexec@lists.infradead.org, wim@iguana.be, LKML , vgoyal@redhat.com, dyoung@redhat.com, Guenter Roeck Subject: Re: [PATCH v3] watchdog: Add hook for kicking in kdump path Message-ID: <20130418174432.GN79013@redhat.com> References: <1366233596-34681-1-git-send-email-dzickus@redhat.com> <87ip3j94qu.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87ip3j94qu.fsf@xmission.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 18, 2013 at 09:35:05AM -0700, Eric W. Biederman wrote: > Don Zickus writes: > > > A common problem with kdump is that during the boot up of the > > second kernel, the hardware watchdog times out and reboots the > > machine before a vmcore can be captured. > > > > Instead of tellling customers to disable their hardware watchdog > > timers, I hacked up a hook to put in the kdump path that provides > > one last kick before jumping into the second kernel. > > Having thought about this a little more this patch is actively wrong. > > The problem is you can easily be petting the watchdog in violation of > whatever policy is normally in place. Which means that this extra > petting can result in a system that is unavailable for an unacceptably > long period of time. Not really, just an extra period which isn't that much. This would only be noticable if kdump is setup and enabled and then _hung_, otherwise it just quickly reboots and noone notices. :-) > > I expect most watchdog policies are not that strict, but this patch > would preclude using those that are. I would assume most of those users would not enable kdump and would not be affected. > > And like is being discussed in another subthread it does look like > changing the timeout and the interval should be enough all on it's own. Probably and I will pursue that. Thanks for the suggestion. Cheers, Don