On 02/13/2014 11:34 AM, Michael wang wrote:
> On 02/12/2014 06:22 PM, Peter Zijlstra wrote:
> [snip]
>>
>> 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.
>
> That sounds better, some thing like this?
Hmm... need a little adjustments, will post formal patch with some test
later.
Regards,
Michael Wang
>
>
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index fb9764f..56a2e1f 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2688,8 +2688,8 @@ need_resched:
> if (prev->on_rq || rq->skip_clock_update < 0)
> update_rq_clock(rq);
>
> - next = pick_next_task(rq, prev);
> clear_tsk_need_resched(prev);
> + next = pick_next_task(rq, prev);
> clear_preempt_need_resched();
> rq->skip_clock_update = 0;
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 235cfa7..48a9500 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4784,7 +4784,18 @@ idle:
> rq->idle_stamp = rq_clock(rq);
> if (idle_balance(rq)) { /* drops rq->lock */
> rq->idle_stamp = 0;
> - goto again;
> + /*
> + * Before we start to pick one of the pulled fair entities, take
> + * care if some RT/DL tasks has been enqueued during the time
> + * we release rq-lock inside idle_balance().
> + *
> + * In such cases, since clear_tsk_need_resched() was done
> + * already, need_resched() will imply the request to sched-in
> + * the enqueued RT/DL tasks, so don't 'goto again' to make sure
> + * the priority.
> + */
> + if (rq->nr_running == rq->cfs.h_nr_running || !need_resched())
> + goto again;
>
>
>
> I like tea BTW, drink every day :)
>
> Regards,
> Michael Wang
>
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