[patch] add kdump_after_notifier

[Takenori Nagano]

Eric W. Biederman wrote:
> Takenori Nagano <t-nagano at ah.jp.nec.com> writes:
>> Hi all,
>>
>> IMHO, most users don't use kdump, kdump users are only kernel developers and
>> enterprise users. 
> 
> Not at all.  So far the only kdump related bug report I have seen has
> been from fedora Core.

Sorry, I thought general users push reset button when the machine is
panicked. :-(

> No.  The problem with your patch is that it doesn't have a code
> impact.  We need to see who is using this and why.

My motivation is very simple. I want to use both kdb and kdump, but I think it
is too weak to satisfy kexec guys. Then I brought up the example enterprise
software. But it isn't a lie. I know some drivers which use panic_notifier.
IMHO, they use only major distribution, and they has the workaround or they
don't notice this problem yet. I think they will be in trouble if all
distributions choose only kdump.

BTW, I use kdb and lkcd now, but I want to use kdb and kdump. I sent a patch to
kdb community but it was rejected. kdb maintainer Keith Owens said,

> 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.

Then I gave up to merge my patch to kdb, and I tried to send another patch to
kexec community. I can understand his opinion, but it is very difficult to
modify that kdump is called from panic_notifier. Because it has a reason why
kdump don't use panic_notifier. So, I made this patch.

Please do something about this problem.

Thanks,