From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1RJmfA-0006NG-FN for kexec@lists.infradead.org; Fri, 28 Oct 2011 13:40:01 +0000 Date: Fri, 28 Oct 2011 09:39:54 -0400 From: Don Zickus Subject: Re: watchdogs and kdump Message-ID: <20111028133954.GS3452@redhat.com> References: <20111027203029.GR3452@redhat.com> <4EA9D09E.800@draigBrady.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4EA9D09E.800@draigBrady.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=twosheds.infradead.org@lists.infradead.org To: =?iso-8859-1?Q?P=E1draig?= Brady Cc: kexec@lists.infradead.org, linux-watchdog@vger.kernel.org, vgoyal@redhat.com, amwang@redhat.com On Thu, Oct 27, 2011 at 10:43:58PM +0100, P=E1draig Brady wrote: > On 10/27/2011 09:30 PM, Don Zickus wrote: > > Hi, > > = > > I was assisting a customer the other day debugging a kdump[1] problem, = when we > > noticed the real problem was the hardware watchdog was firing and > > rebooting the box. > > = > > Of course, this can be inconvienant if the panic happens right before t= he > > watchdog is supposed to be kicked, leading to a spontaneous reboot befo= re > > the second kernel finishes booting and loading the watchdog module. > > = > > I was trying to think of a way to solve this and thought, one way to > > minimize the problem is to kick the watchdog before we jump into the kd= ump > > kernel. Another way is to disable the watchdog entirely, but that does= n't > > work on all hardware I believe. > > = > > Anyway, I was posting on the watchdog mailing list to see if anyone had= any > > ideas that might help. And if my above idea to kick the watchdog before > > jumping into the kdump kernel seems ok, then an api would need to be > > developed. > > = > > I am willing to do any coding and testing necessary, but before I did, I > > wanted help to get a direction to go in first. > > = > > Thoughts? > = > Seems like the appropriate thing to do is to call all the > reboot notifiers that each watchdog registers. > Since one is not doingn a full SYS_RESTART (SYS_DOWN) though, > i.e. not running through the BIOS code again, > it might be worth having a different SYS_JUMP code in notifier.h > that would allow you to kick rather than stop the watchdogs > as the reboot notifiers generally do at the moment. That is an interesting idea. Not sure if calling a blocking notifier in the kdump path would be acceptable to the kexec folks. Then again using the reboot notifier in the panic path may not be a good idea either, it might lead to false expectations. :-/ > I think it would be important not to stop the watchdog if possible, > given the large amount of logic that's going to be executed > after the jump. I agree. Especially since kdump is still not 100% reliable. Thanks for the feedback! Cheers, Don _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec