watchdogs and kdump

[Pádraig Brady]

On 10/27/2011 09:30 PM, Don Zickus wrote:
> Hi,
> 
> I was assisting a customer the other day debugging a kdump[1] problem, when we
> noticed the real problem was the hardware watchdog was firing and
> rebooting the box.
> 
> Of course, this can be inconvienant if the panic happens right before the
> watchdog is supposed to be kicked, leading to a spontaneous reboot before
> the second kernel finishes booting and loading the watchdog module.
> 
> I was trying to think of a way to solve this and thought, one way to
> minimize the problem is to kick the watchdog before we jump into the kdump
> kernel.  Another way is to disable the watchdog entirely, but that doesn't
> work on all hardware I believe.
> 
> Anyway, I was posting on the watchdog mailing list to see if anyone had any
> ideas that might help.  And if my above idea to kick the watchdog before
> jumping into the kdump kernel seems ok, then an api would need to be
> developed.
> 
> I am willing to do any coding and testing necessary, but before I did, I
> wanted help to get a direction to go in first.
> 
> Thoughts?

Seems like the appropriate thing to do is to call all the
reboot notifiers that each watchdog registers.
Since one is not doingn a full SYS_RESTART (SYS_DOWN) though,
i.e. not running through the BIOS code again,
it might be worth having a different SYS_JUMP code in notifier.h
that would allow you to kick rather than stop the watchdogs
as the reboot notifiers generally do at the moment.
I think it would be important not to stop the watchdog if possible,
given the large amount of logic that's going to be executed
after the jump.

cheers,
Pádraig.