Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753716Ab1EIRFm (ORCPT ); Mon, 9 May 2011 13:05:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:22321 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752701Ab1EIRFl (ORCPT ); Mon, 9 May 2011 13:05:41 -0400 Date: Mon, 9 May 2011 13:05:28 -0400 From: Vivek Goyal To: "K.Prasad" Cc: Linux Kernel Mailing List , Andi Kleen , "Luck, Tony" , kexec@lists.infradead.org Subject: Re: [Bug] Kdump does not work when panic triggered due to MCE Message-ID: <20110509170528.GG5975@redhat.com> References: <20110506165412.GB2719@in.ibm.com> <20110509123902.GA5975@redhat.com> <20110509165357.GB1963@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110509165357.GB1963@in.ibm.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 Content-Length: 2598 Lines: 62 On Mon, May 09, 2011 at 10:23:57PM +0530, K.Prasad wrote: > On Mon, May 09, 2011 at 08:39:02AM -0400, Vivek Goyal wrote: > > On Fri, May 06, 2011 at 10:24:12PM +0530, K.Prasad wrote: > > > Hi All, > > > I wanted to test the behaviour of kdump when panic is triggered > > > due to MCE on x86 and found that kdump is not captured. > > > > > > While the kdump service is configured and running and non-MCE panics > > > (such as those triggered through to /proc/sysrq-trigger) successfully > > > capture a kdump, any fatal MCE error injected through the mce-inject > > > tool causes a reboot of the machine. > > > > > > The code has been traced (using early_serial_putc()) to enter the kexec > > > path i.e. panic()->crash_kexec()->machine_kexec()->relocate_kernel() > > > but is untraceable further. > > > > > > Kdump works fine when the same the similar test is carried out inside a > > > KVM guest. > > > > > > Has anybody tested this before? Or have found kdump working when fatal > > > MCEs have actually occurred? > > > > Prasad, > > > > I have never tried taking dump in MCE situation. Does kdump work on this > > machine with normal panic()? > > > > Hi Vivek, > kdump worked fine on this machine for non-MCE triggered panic > calls (the /proc/sysrq-trigger initiated crashes got the kdump fine). > > > Use --debug and --serial option in kexec-tools to print some debug message > > and look for "I am in purgatory". This will tell you whether you hanged > > in first kernel or second kernel. > > > > There were no boot logs from the second kernel while the "Rebooting in X > seconds..." message had appeared before the system rebooted, suggesting > that the second kernel did not boot at all. > > > Then put "outb()" messages in the kernel to trace what happened. > > > > The outb logs showed that the system entered machine_kexec function (traceable > upto relocate_kernel) but then rebooted from inside the panic() function. Ok, that means that we returned from crash_kexec() function instead of transitioning into second kernel. This is strange. machine_kexec() is not supposed to return until and unless it finds that there is no crash kernel loaded. As per your mail you can trace it to relocate_kernel() being entered. So only thing I can suggest is debug relocate_kernel() code now to see why it is returning. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/