RE: [ECOS] Watchdog

[Gary Parnes <GaryP at logicpd dot com>]

A slight twist on the meta-watchdog scheme is to have a high-priority
"system monitor" thread that runs at periodic intervals.  The thread's
responsibility is to monitor the health of all other threads.  First order
of business for the thread: it kicks the watchdog timer. Then, it checks the
system state. If it sees something out of the ordinary, it can try to
correct the system at a software level.  If it determines that the situation
is beyond hope (or merely beyond it's heuristics), it can force an immediate
reset (or let the watchdog expire... either-or).

If either the system timer or the system monitor thread goes out to lunch,
then the watchdog will expire, which is what you would want for this level
of failure.

--Gary Parnes

SENIOR SOFTWARE ENGINEER

Logic Product Development
411 Washington Ave. North, Suite 101
Minneapolis, MN 55401


> -----Original Message-----
> From: Andrew Lunn [mailto:andrew@lunn.ch]
> Sent: Friday, December 17, 2004 10:34 AM
> To: Daniel Gomes
> Cc: ecos-discuss@ecos.sourceware.org
> Subject: Re: [ECOS] Watchdog
> 
> 
> I've also done a meta-watchdog system. I have a high priority thread
> which does the actually kicking. But that thread itself just receives
> kicks from other threads. If any of the other threads stop kicking,
> the "Watchdog" thread stops kicking the hardware.
> 
> Doing it like this i can put kicks into all threads which are
> important so if any one deadlock's we get to know about it. I also put
> one kicker at the lowest priority so that if we reach some sort of
> livelock spinning condition which is eating all the CPU for a while we
> get a reset.
> 
>         Andrew
> 
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