Hello,
On Mon, 11 Jul 2016 13:03:56 +0800
Xunlei Pang <xp...@redhat.com> wrote:
> On 2016/07/08 at 19:28, Juri Lelli wrote:
[...]
> > @@ -363,6 +364,15 @@ static inline void setup_new_dl_entity(struct
> > sched_dl_entity *dl_se, return;
> >
> > /*
> > + * Use the scheduling parameters of the top pi-waiter task,
> > + * if we have one from which we can inherit a deadline.
> > + */
> > + if (dl_se->dl_boosted &&
> > + (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se))) &&
> > + dl_prio(pi_task->normal_prio))
> > + pi_se = &pi_task->dl;
> > +
> > + /*
> > * We use the regular wall clock time to set deadlines in
> > the
> > * future; in fact, we must consider execution overheads
> > (time
> > * spent on hardirq context, etc.).
> > @@ -1721,7 +1731,7 @@ static void switched_from_dl(struct rq *rq,
> > struct task_struct *p) static void switched_to_dl(struct rq *rq,
> > struct task_struct *p) {
> > if (dl_time_before(p->dl.deadline, rq_clock(rq)))
> > - setup_new_dl_entity(&p->dl, &p->dl);
> > + setup_new_dl_entity(&p->dl);
>
> I'm curious why we even call setup_new_dl_entity() for non-queued
> cases? It seems more reasonable to do it when it really gets queued.
> We can see that enqueue_task_dl()->update_dl_entity() also has the
> same update logic as switched_to_dl().
I wondered the same when removing the dl_new field from
sched_dl_entity... But then I realised that enqueue_dl_entity() does
not always invoke update_dl_entity() or replenish_dl_entity()... For
example, when a task switches from SCHED_OTHER (or RT) to -deadline due
to sched_setattr() (or similar) these functions are not invoked.
Luca
> If so, for already queued and boosted cases, rt_mutex_setprio() will
> call enqueue_task() with ENQUEUE_REPLENISH set, so enqueue_dl_entity()
> ->replenish_dl_entity() will advance p->dl.deadline beforehand, see
> code: replenish_dl_entity():
> if (dl_se->dl_deadline == 0) {
> dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
> dl_se->runtime = pi_se->dl_runtime;
> }
>
> IOW, we don't need to handle !dl boosted cases in
> setup_new_dl_entity().
>
> Regards,
> Xunlei
>
> >
> > if (task_on_rq_queued(p) && rq->curr != p) {
> > #ifdef CONFIG_SMP
>
