powerpc/opal: Wake up kopald polling thread before waiting for events

[Benjamin Herrenschmidt]

On Mon, 2016-07-04 at 16:11 +1000, Michael Ellerman wrote:
> On Mon, 2016-04-07 at 04:51:44 UTC, Benjamin Herrenschmidt wrote:
> > On some environments (prototype machines, some simulators, etc...)
> > there is no functional interrupt source to signal completion, so
> > we rely on the fairly slow OPAL heartbeat.
> > 
> > In a number of cases, the calls complete very quickly or even
> > immediately. We've observed that it helps a lot to wakeup the OPAL
> > heartbeat thread before waiting for event in those cases, it will
> > call OPAL immediately to collect completions for anything that
> > finished fast enough.
> 
> Any performance/jitter impact on normal systems?

Not that I can think of.

Cheers,
Ben.