Re: [PATCH 0/2] add new notifier function ,take2

Andrew Morton
2007-10-18T07:41:45Z

On Thu, 18 Oct 2007 15:45:08 +0900 Takenori Nagano <t-nagano@ah.jp.nec.com> wrote:

> Hi,
>
> A big thanks to everybody who read and replied to first version. I have tried to
> incorporate reviewer's comments and suggestions.
>
> changelog take1 -> take2
>
> - Rebased 2.6.23
> - comment updated
> - renamed the notifiner name "tunable_notifier" to "tunable_atomic_notifier"
> - fixed typo
>
>
> These patches add new notifier function and implement it to panic_notifier_list.
> We used the hardcoded notifier chain so far, but it was not flexible. New
> notifier is very flexible, because user can change a list of order by debugfs.
>
> Thanks,
>
> Example)
>
> # cd /sys/kernel/debug/
> # ls
> kprobes pktcdvd
> # insmod ipmi_msghandler.ko
> # ls
> kprobes panic_notifier_list pktcdvd
> # cd panic_notifier_list/
> # ls
> ipmi_msghandler
> # insmod ipmi_watchdog.ko
> # ls
> ipmi_msghandler ipmi_wdog
> # cat ipmi_msghandler/priority
> 200
> # cat ipmi_wdog/priority
> 150
> #
> Kernel panic - not syncing: panic
> ipmi_msghandler : notifier calls panic_event().
> ipmi_watchdog : notifier calls wdog_panic_handler().
>
> .....(reboot)
>
> # cat ipmi_msghandler/priority
> 200
> # cat ipmi_wdog/priority
> 150
> # echo 300 > ipmi_wdog/priority
> #
> Kernel panic - not syncing: panic
> ipmi_watchdog : notifier calls wdog_panic_handler().
> ipmi_msghandler : notifier calls panic_event().

I can sort-of see what this is doing. Runtime-definable management of
which notifier functions will be called on a panic? Or maybe I
misunderstood.

But even if I did understand, I don't understand why Linux needs this
feature - what are the use cases, what is the value to our users?

Can you please flesh that information out a bit more?

The patches are somewhat wordwrapped - please check your email client
configuration, thanks.