jin.dongming at np
Dec 3, 2009, 4:54 PM
Post #3 of 3
(126 views)
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Hi Simon
I am sorry for replying late.
Thank you for your answer and your information.
I will read the discussion and consider whether there is a better method
to resolve my problem.
Best Regards,
Jin Dongming
Simon Kagstrom wrote:
> Hi Jin!
>
> On Thu, 03 Dec 2009 12:04:46 +0900
> Jin Dongming <jin.dongming [at] np> wrote:
>
>> I have a question about kmsg_dump which needs your help.
>> The question is as following:
>> Why not put the kmsg_dump() for OOPS into oops_end() and before the branch
>> of crash_kexec()?
>>
>> The reason for the question is as following:
>> Now the kmsg_dump() for OOPS is added in oops_exit(). When OOPS happened,
>> kernel will call oops_end(). If the crash_kexec() is executed first in
>> oops_end(), the oops_exit() could not be called. And also the kmsg_dump()
>> for PANIC could not be executed. So I think that the kmsg_dump() for OOPS
>> will lose its real meaning.
>
> It would be OK to move it for my part, I understand your reasoning.
> How this is handled seems to vary a bit between architectures though.
> ARM has (arch/arm/kernel/die.c)
>
> NORET_TYPE void die(const char *str, struct pt_regs *regs, int err)
> {
> [...]
> if (panic_on_oops)
> panic("Fatal exception");
>
> oops_exit();
> [...]
>
> while x86 does (arch/x86/kernel/dumpstack.c):
>
> void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
> {
> if (regs && kexec_should_crash(current))
> crash_kexec(regs);
> [...]
> oops_exit();
> [...]
> if (in_interrupt())
> panic("Fatal exception in interrupt");
> if (panic_on_oops)
> panic("Fatal exception");
>
>
> There was some additional discussion on this a while ago in these two
> threads:
>
> http://lkml.org/lkml/2009/11/11/404
>
> http://lkml.org/lkml/2009/10/23/131
>
> where there additionally was a request to move
>
> atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
>
> before kmsg_dump() and crash_kexec(). I can't immediately see any
> problem with this approach, but I'm no expert on kexec. The discussion
> didn't really conclude on this matter though.
>
> // Simon
>
>
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