Re: Bug in scheduler when using rt_mutex

[Yong Zhang]

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