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Subject[patch] DLS: refactor switched_to_dl
From
Though should be splitted, the changes in switched_to_dl and prio_changed_dl
are interleaved, and they are combined just for easing review.

When the priority of task is changed, if it is not the current task, it is
handled by switched_to_dl. Otherwise if prio goes lower, it is rescheduled.

In switched_to_dl, if the given task is either a sleeper or the current task,
we do nothing. And if fail to preempt, we try to push it away.

Signed-off-by: Hillf Danton <dhillf@gmail.com>
---

--- a/kernel/sched_dl.c Mon Apr 9 19:39:56 2012
+++ b/kernel/sched_dl.c Tue Apr 10 21:49:50 2012
@@ -1482,7 +1482,8 @@ static void switched_from_dl(struct rq *
*/
static void switched_to_dl(struct rq *rq, struct task_struct *p)
{
- int check_resched = 1;
+ if (!p->on_rq)
+ return;

/*
* If p is throttled, don't consider the possibility
@@ -1492,53 +1493,32 @@ static void switched_to_dl(struct rq *rq
if (unlikely(p->dl.dl_throttled))
return;

- if (!p->on_rq || rq->curr != p) {
-#ifdef CONFIG_SMP
- if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
- /* Only reschedule if pushing failed */
- check_resched = 0;
-#endif /* CONFIG_SMP */
- if (check_resched && task_has_dl_policy(rq->curr))
- check_preempt_curr_dl(rq, p, 0);
+ if (p == rq->curr)
+ return;
+
+ if (!dl_task(rq->curr)) {
+ check_preempt_curr(rq, p, 0);
+ return;
}
+
+ if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
+ check_preempt_curr_dl(rq, p, 0);
+ return;
+ }
+
+#ifdef CONFIG_SMP
+ if (p->dl.nr_cpus_allowed > 1)
+ if (p == pick_next_pushable_dl_task(rq))
+ push_dl_tasks(rq);
+#endif
}

-/*
- * If the scheduling parameters of a -deadline task changed,
- * a push or pull operation might be needed.
- */
-static void prio_changed_dl(struct rq *rq, struct task_struct *p,
- int oldprio)
+static void prio_changed_dl(struct rq *rq, struct task_struct *p, int oldprio)
{
- if (p->on_rq || rq->curr == p) {
-#ifdef CONFIG_SMP
- /*
- * This might be too much, but unfortunately
- * we don't have the old deadline value, and
- * we can't argue if the task is increasing
- * or lowering its prio, so...
- */
- if (!rq->dl.overloaded)
- pull_dl_task(rq);
-
- /*
- * If we now have a earlier deadline task than p,
- * then reschedule, provided p is still on this
- * runqueue.
- */
- if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) &&
- rq->curr == p)
- resched_task(p);
-#else
- /*
- * Again, we don't know if p has a earlier
- * or later deadline, so let's blindly set a
- * (maybe not needed) rescheduling point.
- */
- resched_task(p);
-#endif /* CONFIG_SMP */
- } else
+ if (p != rq->curr)
switched_to_dl(rq, p);
+ else if (oldprio < p->prio)
+ resched_task(p);
}

static const struct sched_class dl_sched_class = {
--

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