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SubjectRe: [PATCH v5] sched/deadline: support dl task migration during cpu hotplug
Hi Kirill,
On Thu, Nov 13, 2014 at 01:21:31PM +0300, Kirill Tkhai wrote:
>> >>>> @@ -1185,8 +1223,9 @@ static int find_later_rq(struct task_struct *task)
>> >>>> * We have to consider system topology and task affinity
>> >>>> * first, then we can look for a suitable cpu.
>> >>>> */
>> >>>> - cpumask_copy(later_mask, task_rq(task)->rd->span);
>> >>>> - cpumask_and(later_mask, later_mask, cpu_active_mask);
>> >>>> + cpumask_copy(later_mask, cpu_active_mask);
>> >>>> + if (likely(task_rq(task)->online))
>> >>>> + cpumask_and(later_mask, later_mask, task_rq(task)->rd->span);
>> >>>> cpumask_and(later_mask, later_mask, &task->cpus_allowed);
>> >>>> best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
>> >>>> task, later_mask);
>> > Also, we should think about the following situation.
>> >
>> > DL task is left on dead rq. In your scheme it will be moved by the timer.
>> > But what will be if somebody changes the class of the task (before timer)?
>>
>> I think timer will be cancelled in switched_from_dl().
>
>Yeah, but nobody will move this task to alive rq.
>
>>
>> Regards,
>> Wanpeng Li
>>
>> > In this case the task still remains on dead rq.
>> >
>> > We should handle this situation in some way.

Your proposal is a great appreciated.

Regards,
Wanpeng Li

>> >
>> > Kirill
>> >
>> >
>> > --
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