[PATCH] Enable kdump if 2nd-kernel is loaded.

[Ken'ichi Ohmichi]

Hi Simon,

Simon Horman wrote:
> On Thu, Jul 09, 2009 at 04:17:22PM +0900, Ken'ichi Ohmichi wrote:
>> Hi Simon,
>>
>> Thank you so much for your review and comment.
>>
>> I have one question.
>> Should I resend the patch to LKML with your "Acked-by:" tag for merging it ?
>> Or isn't that necessary ?
> 
> I think sending it to LKML with the acked-by would be a good idea.

OK, I will do it.


Thanks
Ken'ichi Ohmichi


>> Simon Horman wrote:
>>> On Thu, Jul 09, 2009 at 09:43:19AM +0900, Ken'ichi Ohmichi wrote:
>>>> Hi Simon,
>>>>
>>>> Thank you for the comment.
>>>>
>>>> Simon Horman wrote:
>>>>> On Wed, Jul 08, 2009 at 01:38:59PM +0900, Ken'ichi Ohmichi wrote:
>>>>>> Hi,
>>>>>>
>>>>>> This patch enables a kdump if 2nd-kernel is loaded.
>>>>>> (The patch is based on linux-2.6.31-rc2.)
>>>>>>
>>>>>> Now, a kdump is enabled if a kernel parameter "oops=panic" is specified and
>>>>>> 2nd-kernel is loaded. I think that a kdump should be enabled regardless of
>>>>>> "oops=panic" if 2nd-kernel is loaded, because a system administrator loads
>>>>>> 2nd-kernel for enabling a kdump.
>>>>> I'm not sure that I like this change. To my mind, panic on oops
>>>>> should only occur if specifically requested.
>>>> My patch does not make panic_on_oops effective when 2nd-kernel is loaded,
>>>> and it makes a kdump effective.
>>>>
>>>> kexec_should_crash() is called only by oops_end() for checking whether to
>>>> call crash_kexec(). crash_kexec() is not panic, and I feel it is better
>>>> that crash_kexec() is called when 2nd-kernel is loaded.
>>>>
>>>>
>>>> I tried to test a kdump on linux-2.6.31-rc1 *without* a kernel parameter
>>>> "oops=panic" by `echo c > /proc/sysrq-trigger`, but a kdump did not work
>>>> because a kdump, which is occurred by `echo c > /proc/sysrq-trigger`, has
>>>> been changed to a NULL pointer error instead of calling crash_kexec()
>>>> since linux-2.6.31-rc1. Then I tried to boot linux-2.6.31-rc1 *with* a
>>>> kernel parameter "oops=panic", the kernel got a panic while kernel booting
>>>> due to a problem other than a kdump. 
>>>> So I think a kdump should be enabled when 2nd-kernel is loaded.
>>> Hi,
>>>
>>> thanks for the more detailed explanation. I've reconsidered my position
>>> and actually I think that I quite like your idea - it does indeed make
>>> sense for kdump to occur if a kdump kernel has been loaded.
>>>
>>> Acked-by: Simon Horman <horms at verge.net.au>
>>>
>>>> Thanks
>>>> Ken'ichi Ohmichi
>>>>
>>>>>> Signed-off-by: Ken'ichi Ohmichi <oomichi at mxs.nes.nec.co.jp>
>>>>>> ---
>>>>>> --- a/kernel/kexec.c	2009-07-08 12:30:26.000000000 +0900
>>>>>> +++ b/kernel/kexec.c	2009-07-08 12:38:08.000000000 +0900
>>>>>> @@ -57,6 +57,8 @@ struct resource crashk_res = {
>>>>>>  
>>>>>>  int kexec_should_crash(struct task_struct *p)
>>>>>>  {
>>>>>> +	if (kexec_crash_image)
>>>>>> +		return 1;
>>>>>>  	if (in_interrupt() || !p->pid || is_global_init(p) || panic_on_oops)
>>>>>>  		return 1;
>>>>>>  	return 0;
>>>>>>
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>>>>>
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