On Wed, Feb 12, 2014 at 02:26:25PM +0800, Michael wang wrote:
> Hi, Peter
>
> On 02/11/2014 08:17 PM, tip-bot for Peter Zijlstra wrote:
> [snip]
> > +
> > +idle:
> > +#ifdef CONFIG_SMP
> > + idle_enter_fair(rq);
> > + /*
> > + * We must set idle_stamp _before_ calling idle_balance(), such that we
> > + * measure the duration of idle_balance() as idle time.
> > + */
> > + rq->idle_stamp = rq_clock(rq);
> > + if (idle_balance(rq)) { /* drops rq->lock */
>
> Since idle_balance() will release the rq lock, will it happen that some
> rt or dl tasks was waken up and enqueued before it hold the lock again?
>
> Should we recheck 'rq->nr_running == rq->cfs.h_nr_running' here before
> goto pick fair entity to make sure the priority?
>
> May be like:
>
> if (idle_balance(rq) &&
> rq->nr_running == rq->cfs.h_nr_running)
Yes I think there might be a problem here because of how we re-arranged
things. Let me brew of pot of tea and try to actually wake up.
I suspect we might be good if we clear the need_resched flags before
calling pick_next_task. Then any RT/DL task that gets moved here will
set need resched, and we'll retry the pick_next_task loop.
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|