Re: [RFC PATCH v3] sched/deadline: support dl task migration during cpu hotplug

[Wanpeng Li]

Hi Peter,
On 14/11/11 äå7:33, Peter Zijlstra wrote:
> On Thu, Nov 06, 2014 at 10:40:49AM +0800, Wanpeng Li wrote:
> > @@ -538,6 +539,46 @@ again:
> >   	update_rq_clock(rq);
> >   	dl_se->dl_throttled = 0;
> >   	dl_se->dl_yielded = 0;
> > +
> > +	/*
> > +	 * So if we find that the rq the task was on is no longer
> > +	 * available, we need to select a new rq.
> > +	 */
> > +	if (!rq->online) {
> > +		struct rq *later_rq = NULL;
> > +
> > +		raw_spin_unlock(&rq->lock);
> > +
> > +		later_rq = find_lock_later_rq(p, rq);
> > +
> > +		if (!later_rq) {
> > +			int cpu;
> > +
> > +			/*
> > +			 * If cannot preempt any rq, fallback to pick any
> > +			 * online cpu.
> > +			 */
> > +			for_each_cpu(cpu, &p->cpus_allowed)
> > +				if (cpu_online(cpu))
> > +					later_rq = cpu_rq(cpu);
> 			cpu = cpumask_any_and(cpu_active_mask, tsk_cpus_allowed(p));
> 			if (cpu >= nr_cpu_ids)
> 				/* fail */
>
> 			later_rq = cpu_rq(cpu);

Ok.

> > +			if (!later_rq) {
> > +				pr_warn("fail to find any online and task
> > +						will never come back to us\n");
> > +				goto out;
> > +			}
> > +		}
> > +
> > +		deactivate_task(rq, p, 0);
> > +		set_task_cpu(p, later_rq->cpu);
> > +		activate_task(later_rq, p, 0);
> > +
> > +		resched_curr(later_rq);
> > +
> > +		double_unlock_balance(rq, later_rq);
> > +
> > +		goto out;
> > +	}
> > +
> >   	if (task_on_rq_queued(p)) {
> >   		enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
> >   		if (dl_task(rq->curr))
> > @@ -555,7 +596,7 @@ again:
> >   	}
> >   unlock:
> >   	raw_spin_unlock(&rq->lock);
> > -
> > +out:
> >   	return HRTIMER_NORESTART;
> >   }
> >   
> > @@ -1185,8 +1226,12 @@ 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);
> > +	if (likely(task_rq(task)->online)) {
> > +		cpumask_copy(later_mask, task_rq(task)->rd->span);
> > +		cpumask_and(later_mask, later_mask, cpu_active_mask);
> > +	} else
> > +		/* for offline cpus we have a singleton rd */
> > +		cpumask_copy(later_mask, cpu_active_mask);
> >   	cpumask_and(later_mask, later_mask, &task->cpus_allowed);
> >   	best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
> >   			task, later_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);
>
> Is the same, right and less lines.

Thanks for your great help! I will fold these to my patch and send out a 
newer version tomorrow. ;-)

Regards,
Wanpeng Li

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