Re: perf_events: proposed fix for broken intr throttling (repost)

[Peter Zijlstra]

On Wed, 2012-01-04 at 21:33 +0000, Stephane Eranian wrote:
> > I don't think it needs that, I do dislike the unconditional iterate all
> > events thing though. Maybe we can set some per-cpu state indicating
> > someone got throttled (rare under normal operation -- you'd hope) and
> > only iterate to unthrottle when we find this set.
> >
> Could try that too.
> 
> > I think the event scheduling resulting from migration will already
> > re-enable the event, avoiding the loss of unthrottle due to that..
> > although it would be good to verify that.
> >
> Yes, you're not dead forever, but still it is not acceptable as is. 

Oh for sure, I didn't mean it like that. What I was getting at is a
counter getting throttled on one cpu, setting the per-cpu variable,
getting migrated and not getting unthrottled due to now living on
another cpu which doesn't have the per-cpu thing set.

If the scheduling resulting from the migration already unthrottles that
scenario can't happen.

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