linux-kernel - Re: Bug in scheduler when using rt

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Date:	Thu, 20 Jan 2011 12:18:14 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	samu.p.onkalo@...ia.com, mingo@...e.hu,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	tglx <tglx@...utronix.de>, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: Bug in scheduler when using rt_mutex

On Wed, Jan 19, 2011 at 9:30 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> +static void switched_from_fair(struct rq *rq, struct task_struct *p)
> +{
> +       struct sched_entity *se = &p->se;
> +       struct cfs_rq *cfs_rq = cfs_rq_of(se);
> +
> +       /*
> +        * Ensure the task's vruntime is normalized, so that when its
> +        * switched back to the fair class the enqueue_entity(.flags=0) will
> +        * do the right thing.
> +        *
> +        * If it was on_rq, then the dequeue_entity(.flags=0) will already
> +        * have normalized the vruntime, if it was !on_rq, then only when
> +        * the task is sleeping will it still have non-normalized vruntime.
> +        */
> +       if (!se->on_rq && p->state != TASK_RUNNING)
> +               se->vruntime -= cfs_rq->min_vruntime;

Here it's possible that se->vruntime is little than cfs_rq->min_vruntime.

Thanks,
Yong

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Only stand for myself
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