linux-kernel - Question about kmsg

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Date:	Thu, 03 Dec 2009 12:04:46 +0900
From:	Jin Dongming <jin.dongming@...css.fujitsu.com>
To:	Simon Kagstrom <simon.kagstrom@...insight.net>
CC:	LKLM <linux-kernel@...r.kernel.org>
Subject: Question about kmsg_dump for OOPS

Hello, Simon

I am Jin Dongming.

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.
    
    The function tree for OOPS is as following:
      oops_end()
        |
        |-- if (crash_kexec is valid)
        |      |
        |      |-- crash_kexec()    ==> reboot (and the following function will
        |                                       not be executed)
        |
        |-- oops_exit
        |      |
        |      |-- kmsg_dump(OOPS)
        |
        |-- if (panic is valid)
        |      |
        |      |-- kmsg_dump(PANIC)
        |

    The function tree for PANIC is as following:
      panic()
        |
        |-- kmsg_dump(PANIC)
        |
        |-- crash_kexec()
        |
        |-- notifier()


When kernel paniced, kmsg_dump() for PANIC is executed before crash_kexec(). So
I think before crash_kexec() is executed, kmsg_dump() for OOPS should be called
too. How do you think?

Best regards,
Jin Dongming

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