Re: [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers

[Peter Zijlstra]

On Thu, Aug 08, 2019 at 10:46:52AM +0200, Juri Lelli wrote:
> On 08/08/19 10:11, Dietmar Eggemann wrote:

> > What about the fast path in pick_next_task()?
> > 
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index bffe849b5a42..f1ea6ae16052 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -3742,6 +3742,9 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
> >                 if (unlikely(!p))
> >                         p = idle_sched_class.pick_next_task(rq, prev, rf);
> >  
> > +               if (p->sched_class == &fair_sched_class && p->server)
> > +                       p->server = NULL;
> > +
> 
> Hummm, but then who sets it back to the correct server. AFAIU
> update_curr() needs a ->server to do the correct DL accounting?

The above looks ok.

The pick_next_task_dl() when it selects a server will set ->server.