[patch] Fix some problem between kdb and kdump

Takenori Nagano t-nagano at ah.jp.nec.com
Thu May 31 18:49:21 PDT 2007

Hi Keith,

I agree with your opinion.
But we can't choose LKCD after 2.6.18.

LKCD maintainer Troy said
> On 04/25/07 19:23, Sébastien CRAMATTE wrote:
>> > how can I use lkcd with kernel >= 2.6.18
> The general suggestion is to use KDUMP which is already included in
> stock kernel >= 2.6.18. See Documentation/kdump/kdump.txt in your
> kernel source tree for more information about kdump.
> Troy

Kdump has many problems, but we can't choose other choices after 2.6.18.
IMHO, we have to modify kdb that we can use both kdb and kdump after 2.6.18.

Keith, do you have any idea to resolve this?

Keith Owens wrote:
> Takenori Nagano (on Thu, 31 May 2007 16:37:59 +0900) wrote:
>> Hi,
>> kdb has some problem to use with kdump.
>> This patch fixes some of them.
>> 1) We can't use kdb when machine panicked.
>> crash_kexec() is called before notifier_call_chain(&panic_notifier_chain)=
>> .
>> This patch makes KDB_ENTER() is called before crash_kexec().
> Both KDB and crash_kexec should be using the panic_notifier_chain, with
> KDB having a higher priority than crash_exec.  The whole point of
> notifier chains is to handle cases like this, so we should not be
> adding more code to the panic routine.
> The real problem here is the way that the crash_exec code is hard coded
> into various places instead of using notifier chains.  The same issue
> exists in arch/ia64/kernel/mca.c because of bad coding practices from
> kexec.
>> 2) We can't take a kdump when KDB_FLAG is set CATASTROPHIC.
>> kdb_do_dump() does not support kdump.
>> This patch makes machine_kexec() is called from kdb_do_dump().
> Ugly.  All the code for selecting which dump to take (lkcd, kexec,
> anything else) should be in a common kernel routine that anybody can
> call.  It should not be just in KDB.
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