Re: handling watchdog in SMP

[Kumar Gala]

On Oct 25, 2007, at 2:37 PM, Wim Van Sebroeck wrote:
> Hi Kumar,
>
> > I was hoping to get some ideas on how to handle the watchdog timers
> > we have on some embedded PPC (booke_wdt.c) cores when we are in a SMP
> > system.
> >
> > The problem is since the watchdog is part of the processor core
> > depending on which processor a given system call is executed at we
> > might get different behavior.  It seems like we would want to mirror
> > the actions to both cores (via smp_call_function).
> >
> > Looking at the file ops we currently support in booke_wdt.c it seems
> > like we could mirror the actions for booke_wdt_write()/booke_wdt_ping
> > () to both cores and ensure when we set something like
> > WDIOC_SETTIMEOUT we set the registers in both processors.
> >
> > I was wondering if anyone had any other ideas or if this model seems
> > to work.
>
> I see 2 ways to go:
> 1) short term: make sure that your actions are duplicated to both  
> cores
> (like you said). At least then you are protected if your complete  
> system
> crashes.
> 2) I'm working on the uniform/generic watchdog device driver. Phase  
> 1 is
> the "new" api and the /dev/watchdog handling. Phase 2 is a sysfs  
> interface.
> Phase 3 is to allow multiple devices (and there I'm still thinking  
> about
> how the /dev/watchdog interface should work).
> But the general idea is to allow at least the control of each watchdog
> device by the sysfs interface.

I haven't been following watchdog subsystem development and was  
wondering if any progress has been made on #2?

- k
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