Re: [PATCH v2 7/7] sched/rt: reschedule if stop/dl task slip in after pull operations

[Wanpeng Li]

On 5/29/15 10:34 PM, Peter Zijlstra wrote:
> On Wed, May 13, 2015 at 02:01:07PM +0800, Wanpeng Li wrote:
> > pull_rt_task() can drop (and re-acquire) rq->lock, this means a dl
> > or stop task can slip in, in which case need to reschedule. This
> > patch add the reschedule when the scenario occurs.
> >
> > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
> > ---
> >   kernel/sched/rt.c | 19 ++++++++++++++++++-
> >   1 file changed, 18 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> > index 560d2fa..8c948bf 100644
> > --- a/kernel/sched/rt.c
> > +++ b/kernel/sched/rt.c
> > @@ -2136,7 +2136,14 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
> >   	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
> >   		return;
> >   
> > -	if (pull_rt_task(rq))
> > +	/*
> > +	 * pull_rt_task() can drop (and re-acquire) rq->lock; this
> > +	 * means a dl or stop task can slip in, in which case we need
> > +	 * to reschedule.
> > +	 */
> > +	if (pull_rt_task(rq) ||
> > +		(unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
> > +			rq->dl.dl_nr_running)))
> >   		resched_curr(rq);
> >   }
> Same as before; why is the normal wakeup preemption check not working?

I will drop these two patches and send out v3. :)

Regards,
Wanpeng Li

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