From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261377AbVGGMX3 (ORCPT ); Thu, 7 Jul 2005 08:23:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261385AbVGGMST (ORCPT ); Thu, 7 Jul 2005 08:18:19 -0400 Received: from mail.metronet.co.uk ([213.162.97.75]:22742 "EHLO mail.metronet.co.uk") by vger.kernel.org with ESMTP id S261303AbVGGMPY (ORCPT ); Thu, 7 Jul 2005 08:15:24 -0400 From: Alistair John Strachan To: Ingo Molnar Subject: Re: Realtime Preemption, 2.6.12, Beginners Guide? Date: Thu, 7 Jul 2005 13:15:24 +0100 User-Agent: KMail/1.8.1 Cc: linux-kernel@vger.kernel.org References: <200507061257.36738.s0348365@sms.ed.ac.uk> <200507071237.42470.s0348365@sms.ed.ac.uk> <20050707114223.GA29825@elte.hu> In-Reply-To: <20050707114223.GA29825@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200507071315.24669.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 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). Is this any help do you? -- 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.