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On Thu, 27 May 2010, Milton Miller wrote:

>
> [Hmm, why did this not appear in patchwork.kernel.org? Now
> I have to guess a CC list.]
>
> On Wed, 26 May 2010 around 22:43:50 -0400 (EDT), Len Brown wrote:
> > From: Len Brown <len.brown@intel.com>
> >
> > TS_POLLING set tells the scheduler a task will poll
> > need_resched() to look for work.
> >
>
> True
>
> > TS_POLLING clear tells resched_task() and wake_up_idle_cpu()
> > that the remote CPU is sleeping in idle, and thus requires
> > a reschedule interrupt to wake them to notice work.
>
> No, that only applies to the idle task.
>
>
> >
> > Update the description of TS_POLLING to reflect how it works.
> > "cleared when sleeping in idle, requiring reschedule interrupt"
>
> That would imply its set for every normal task that is not in some
> kind of sleep state.

you're right, just the idle task sets this flag.

> > Signed-off-by: Len Brown <len.brown@intel.com>
> > Acked-by: Peter Zijlstra <peterz@infradead.org>
>
> > -#define TS_POLLING 0x0004 /* true if in idle loop
> > - and not sleeping */
> > +#define TS_POLLING 0x0004 /* clear when sleeping in idle
> > + requiring reschedule interrupt */
>
> How about "idle task polling need_resched, skip sending interrupt"?

I think that is an improvement over my wording.

Though technically we're not polling need_resched in the case
I have in mind. The hardware is snooping any write to the thread flags
via MONITOR/MWAIT trigger address.

cheers,
-Len Brown, Intel Open Source Technology Center






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