[PATCH] ARM: kexec: offline non panic CPUs on Kdump panic

Vijay Kilari vijay.kilari at gmail.com
Mon Aug 12 08:18:38 EDT 2013

On Thu, Aug 1, 2013 at 9:55 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> On 08/01/2013 07:49 AM, Vijay Kilari wrote:
>> On Wed, Jul 31, 2013 at 10:44 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>> On 07/31/2013 05:37 AM, Vijay Kilari wrote:
>>>> On Tue, Jul 30, 2013 at 10:29 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>>>> On 07/30/2013 04:37 AM, Vijay Kilari wrote:
>>>>>> On Fri, Jul 26, 2013 at 10:38 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>>>> ...
>>>>>>> Does a kernel that's used as the crash kernel guarantee:
>>>>>>> * Never to re-use the memory that was used by the previous kernel, so
>>>>>>> that the spin loop code/data won't be corrupted, ever, no matter how
>>>>>>> long the crash recovery kernel runs.
>>>>>>> * Not use SMP, so there's never a need to re-activate the non-boot CPUs,
>>>>>>> which might not work if they aren't truly disabled but rather just
>>>>>>> running a pin loop?
>>>>>> From cat /proc/iomem, normal kernel is executed from (0x80xxxxxx) with crash
>>>>>> kernel reserved 64M at 0xa0000000
>>>>>> 80000000-bfffffff : System RAM
>>>>>>   80008000-805aeddf : Kernel code
>>>>>>   805e2000-8063e427 : Kernel data
>>>>>>   a0000000-a3ffffff : Crash kernel
>>>>>> crash kernel is loaded to reserved memory location and is executed from there.
>>>>>> I could confirm this from /proc/iomem when crash kernel is running
>>>>>> a0000000-a3efffff : System RAM
>>>>>>   a0008000-a05aeddf : Kernel code
>>>>>>   a05e2000-a063e427 : Kernel data
>>>>> OK, but in the crash dump kernel, is 80008000..8063e427 reserved as
>>>>> well, which would guarantee that the spin loop being executed by the
>>>>> non-crash CPUs won't be corrupted?
>>>> The crash dump kernel runs from reserved memory area (0xa0000000 - 0xa3effffff).
>>>>  So it should not corrupt the memory area of original kernel that was running
>>>>  at 0x80000000,where other CPU's are in spin loop.
>>> What about dynamic allocations?
>> IMHO, it is the kdump functionality to ensure that it won't corrupt
>> original kernel's dynamic allocations
> OK, if there are explicit measure to assure this already, then there's
> no issue.

Hi Will,

 Can you please consider this patch?

Thanks & Regards

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