Date: Mon, 9 May 2011 22:23:57 +0530
From: "K.Prasad" <prasad@linux.vnet.ibm.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>, "Luck, Tony" <tony.luck@intel.com>,
        kexec@lists.infradead.org
Subject: Re: [Bug] Kdump does not work when panic triggered due to MCE
Message-ID: <20110509165357.GB1963@in.ibm.com>
Reply-To: prasad@linux.vnet.ibm.com
References: <20110506165412.GB2719@in.ibm.com>
 <20110509123902.GA5975@redhat.com>
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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.

Thanks,
K.Prasad

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