linux-kernel - Re: kdump broken on 2.6.37-rc4

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Date:	Wed, 8 Dec 2010 15:19:43 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Maxim Uvarov <muvarov@...il.com>,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Neil Horman <nhorman@...hat.com>
Subject: Re: kdump broken on 2.6.37-rc4

On Tue, Dec 07, 2010 at 11:24:46AM -0800, Yinghai Lu wrote:
> On 12/07/2010 02:50 AM, Stanislaw Gruszka wrote:
> > On Fri, Dec 03, 2010 at 12:54:01PM -0500, Neil Horman wrote:
> >> On Fri, Dec 03, 2010 at 06:11:48PM +0100, Stanislaw Gruszka wrote:
> >>> On Fri, Dec 03, 2010 at 06:46:09PM +0300, Maxim Uvarov wrote:
> >>>> 2010/12/3 Stanislaw Gruszka <sgruszka@...hat.com>:
> >>>>> On my T-60 laptop, i686 system with 2.6.37-rc4 kernel,
> >>>>> "echo c > /proc/sysrq-trigger" just hung the system. Kdump
> >>>>> works on 2.6.36. Is this known issue? If not, what info
> >>>>> I should provide to solve it (I think the easiest way
> >>>>> to solve the problem would be bisect) ?
> >>>>>
> >>>>> Stanislaw
> >>>>>
> >>>>
> >>>> I tested x86 QEMU yesterday with the latest git. It worked.
> >>>> Might be something target specific.., What does console print?
> >>>
> >>> Here is the photo 
> >>> http://people.redhat.com/sgruszka/20101203_005.jpg
> >>>
> >>> There are two BUGs, first "sleeping function called from invalid
> >>> context" and then "unable to handle null pointer dereference".
> >>>
> >> The warning about sleeping is an artifact of the fact that we panic the box with
> >> irqs disabled I think (although I would think the fault handler would have
> >> re-enabled them properly).  Not sure what the NULL pointer is from
> > 
> > NULL pointer dereferece is ok, that's the way sysrq_handle_crash
> > trigger a crash. Problem here is that secondary kdump kernel hung at
> > start.
> > 
> > Bisection shows that bad commit is
> > 
> > commit 72d7c3b33c980843e756681fb4867dc1efd62a76
> > Author: Yinghai Lu <yinghai@...nel.org>
> > Date:   Wed Aug 25 13:39:17 2010 -0700
> 
> please check debug patches, and boot first kernel and kexec second kernel with "ignore_loglevel debug earlyprintk...."

Second kernel does not print anything, so maybe it not even start.
Dmesg from primary kernel attached.

Stanislaw

View attachment "t60.dmesg" of type "text/plain" (56932 bytes)