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SubjectRe: scheduling problem?
Mike Galbraith wrote:
>
> On Wed, 3 Jan 2001, Daniel Phillips wrote:
>
> > Mike Galbraith wrote:
> > > Semaphore timed out during boot, leaving bdflush as zombie.
> >
> > Wait a sec, what do you mean by 'semaphore timed out'? These should
> > wait patiently forever.
>
> IKD has a semaphore deadlock detector.

That was my tentative conclusion.

> Any place you take a semaphore
> and have to wait longer than 5 seconds (what I had it set to because
> with trace buffer set to 3000000 entries, it can only cover ~8 seconds
> of disk [slowest] load), it triggers and freezes the trace buffer for
> later use. It firing under load may not be of interest. (but it firing
> looks to be very closly coupled to observed stalls with virgin source.
> Linus fixes big stall and deadlock detector mostly shuts up. I fix a
> smaller stall and it shuts up entirely.. for this workload)

But it's entirely legal for a semaphore to wait forever when used in the
way I've used them, a producer/consumer pattern. You should be able to
run happily (at least as happily as before) with the watchdog disabled.

This begs the question of what to do about the 99.99% of cases where the
watchdog is a good thing to have. Shouldn't the watchdog just log the
'suspicious' event and continue?

--
Daniel
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