On Thu, Oct 27, 2011 at 10:43:58PM +0100, P?draig Brady wrote: > 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. That is an interesting idea. Not sure if calling a blocking notifier in the kdump path would be acceptable to the kexec folks. Then again using the reboot notifier in the panic path may not be a good idea either, it might lead to false expectations. :-/ > 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. I agree. Especially since kdump is still not 100% reliable. Thanks for the feedback! Cheers, Don
