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SubjectRe: Timer interrupt stops, causes soft lockup
Hi!

> Of course when time stops progessing forward at a steady pace all
> sorts of Bad Things happen.
>
> The clock loop is caused by jiffies not incrementing. It seems that wall
> time updates itself and then resync's with jiffies every ~4s.
>
> We verified that all spinlocks ( xtime_lock in particular ) were not
> being held, and that the kernel had no reason not to update jiffies.
> Other interrupts continue to fire, so we're not stuck in the timer
> handler.
>
> So, we went on to look at the PIC. We threw together a little kernel
> module to get some debug info.

Nice debugging.

> We have over 10 systems demonstrating the problem, many in customer
> sites.

Does nosmp help?

Does noapic/nolapic help?

You may want to try testing with HZ=4000... to show the problem
faster.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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