From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261315AbVGGMeM (ORCPT ); Thu, 7 Jul 2005 08:34:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261365AbVGGMeL (ORCPT ); Thu, 7 Jul 2005 08:34:11 -0400 Received: from mail.metronet.co.uk ([213.162.97.75]:25306 "EHLO mail.metronet.co.uk") by vger.kernel.org with ESMTP id S261315AbVGGMdy (ORCPT ); Thu, 7 Jul 2005 08:33:54 -0400 From: Alistair John Strachan To: Ingo Molnar Subject: Re: Realtime Preemption, 2.6.12, Beginners Guide? Date: Thu, 7 Jul 2005 13:33:55 +0100 User-Agent: KMail/1.8.1 Cc: linux-kernel@vger.kernel.org References: <200507061257.36738.s0348365@sms.ed.ac.uk> <20050707114223.GA29825@elte.hu> <200507071315.24669.s0348365@sms.ed.ac.uk> In-Reply-To: <200507071315.24669.s0348365@sms.ed.ac.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200507071333.56016.s0348365@sms.ed.ac.uk> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 07 Jul 2005 13:15, Alistair John Strachan wrote: > On Thursday 07 Jul 2005 12:42, Ingo Molnar wrote: > > * Alistair John Strachan wrote: > > > > do you have DEBUG_STACKOVERFLOW and latency tracing still enabled? > > > > The combination of those two options is pretty good at detecting > > > > stack overflows. Also, you might want to enable CONFIG_4KSTACKS, that > > > > too disturbs the stack layout enough so that the error message may > > > > make it to the console. > > > > > > I already have 4KSTACKS on. Latency tracing is enabled, but > > > STACKOVERFLOW isn't; I'll just reenable everything again until we fix > > > this. Do you think if I removed the printk() line I might get some > > > useful information, before it does the stack trace? > > > > usually such loops happen if the stack has been overflown and critical > > information that lies on the bottom of the stack (struct thread_info) is > > overwritten. Then we often cannot even perform simple printks. Stack > > overflow debugging wont prevent the crash, but might give a better > > traceback. > > > > Ingo > > http://devzero.co.uk/~alistair/oops1.jpeg > > I disabled the trace and the STACKOVERFLOW option seems to help; I've got a > (slightly truncated) oops from the kernel. What happens is that I get an > oops, then I get a BUG: warning me about the softlock, then I get another > oops. I'm about to reboot to confirm whether the second oops is identical > to the first (I suspect that it is). http://devzero.co.uk/~alistair/oops3.jpeg This shows the first oops (it's slightly different). http://devzero.co.uk/~alistair/oops2.jpeg This shows the BUG: after the first oops -- Cheers, Alistair. personal: alistair()devzero!co!uk university: s0348365()sms!ed!ac!uk student: CS/CSim Undergraduate contact: 1F2 55 South Clerk Street, Edinburgh. EH8 9PP.