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Message-ID: <20091203092622.599b3814@marrow.netinsight.se>
Date: Thu, 3 Dec 2009 09:26:22 +0100
From: Simon Kagstrom <simon.kagstrom@...insight.net>
To: Jin Dongming <jin.dongming@...css.fujitsu.com>
Cc: LKLM <linux-kernel@...r.kernel.org>
Subject: Re: Question about kmsg_dump for OOPS
Hi Jin!
On Thu, 03 Dec 2009 12:04:46 +0900
Jin Dongming <jin.dongming@...css.fujitsu.com> 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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