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

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Date:	Tue, 07 Dec 2010 11:24:46 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Stanislaw Gruszka <sgruszka@...hat.com>
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 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...."

Thanks

	Yinghai

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