linux-kernel - Re: [PATCH RFC] sched/deadline: support dl task migrate during cpu hotplug

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Date:	Tue, 4 Nov 2014 16:46:23 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Wanpeng Li <kernellwp@...il.com>
Cc:	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Kirill Tkhai <ktkhai@...allels.com>,
	Juri Lelli <juri.lelli@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] sched/deadline: support dl task migrate during cpu
 hotplug

On Tue, Nov 04, 2014 at 09:30:46PM +0800, Wanpeng Li wrote:


> + if (!rq->online) {
> + struct rq *latest_rq = NULL;
> + int cpu;
> + u64 dmin = LONG_MAX;
> +
> + for_each_cpu(cpu, &p->cpus_allowed)
> + if (cpu_online(cpu) &&
> + cpu_rq(cpu)->dl.earliest_dl.curr < dmin) {
> + latest_rq = cpu_rq(cpu);
> + dmin = latest_rq->dl.earliest_dl.curr;
> + }

I would have expected something using find_later_rq(), but I might be
mistaken, I'll let Juri suggest something.

> +
> + if (!latest_rq)
> + goto unlock;
> +
> + raw_spin_lock(&latest_rq->lock);
> +
> + deactivate_task(rq, p, 0);
> + set_task_cpu(p, latest_rq->cpu);
> + activate_task(latest_rq, p, 0);
> +
> + raw_spin_unlock(&latest_rq->lock);
> + }
> +
> unlock:
> raw_spin_unlock(&rq->lock);
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