On Tue, Jun 17, 2014 at 07:27:31PM -0700, Andi Kleen wrote:
> > OK. What would you suggest instead? If all we do is to revert the
>
> Hang checker should have two timer phases:
>
> Timer fires first time:
> - Save context switch counter on that. Force a reschedule to some
> work queue. Rearm timer
>
> Timer fires again:
> - Check reschedule count. If the reschedule count changed
> it was a real hang, otherwise ignore.
I could take that approach, but the RT guys aren't going to thank me for
the wakeup associated with the work queue. I suppose that I could use
one approach for real-time workloads and your workqueue-base approach
for other workloads.
Still, I bet I can drop the common-case cond_resched() overhead to a
single read of a per-CPU variable and a branch. But yes, that would be
in response to the second phase, FWIW. If that measurably too much
overhead, then one thing for realtime and another otherwise.
Thanx, Paul
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