Re: [PATCH 06/16] sched: SCHED_DEADLINE push and pull logic

[Peter Zijlstra]

On Wed, 2012-04-11 at 12:33 -0400, Steven Rostedt wrote:
> On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
> >  
> > @@ -543,6 +897,9 @@ static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
> >  {
> >  	update_curr_dl(rq);
> >  	p->se.exec_start = 0;
> > +
> > +	if (on_dl_rq(&p->dl) && p->dl.nr_cpus_allowed > 1)
> > +		enqueue_pushable_dl_task(rq, p);
> >  }
> 
> Ouch! We need to fix this. This has nothing to do with your patch
> series, but if you look at schedule():
> 
> 	put_prev_task(rq, prev);
> 	next = pick_next_task(rq);
> 
> 
> We put the prev task and then pick the next task. If we call schedule
> for some reason when we don't need to really schedule, then we just
> added and removed from the pushable rb tree the same task. That is, we
> did the rb manipulation twice, for no good reason.
> 
> Not sure how to fix this. But it will require a generic change.


Something like so: https://lkml.org/lkml/2012/2/16/487 ?
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