Re: [PATCH v2 2/3] sched/dl: Cleanup prio_changed_dl()

Kirill Tkhai
2014-10-02T09:52:27Z

В Чт, 02/10/2014 в 11:36 +0200, Peter Zijlstra пишет:
> On Wed, Oct 01, 2014 at 01:04:35AM +0400, Kirill Tkhai wrote:
> > From: Kirill Tkhai <ktkhai@parallels.com>
> >
> > rq->curr task can't be in "dequeued" state in prio_changed_dl().
> > (The only place we can have that is __schedule()). So, we delete
> > rq->curr check.
>
> the CBS timer can throttle it right?

Yeah, it's better to check for on_dl_rq():

[PATCH]sched/dl: Cleanup prio_changed_dl()

rq->curr task can't be in "dequeued" state in prio_changed_dl().
(The only place we can have that is __schedule()). So, we delete
rq->curr check.

We shouldn't do balancing if deadline task is throttled too.

Also delete "else" branch which is dead code (switched_to_dl()
is not interested in dequeued tasks and we are not interested
in balancing in this case).

Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 63f8b4a..ccea917 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1638,35 +1638,33 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
static void prio_changed_dl(struct rq *rq, struct task_struct *p,
int oldprio)
{
- if (task_on_rq_queued(p) || rq->curr == p) {
+ if (!on_dl_rq(&p->dl))
+ return;
#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_curr(rq);
-#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.
- */
+ /*
+ * 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_curr(rq);
+#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_curr(rq);
#endif /* CONFIG_SMP */
- } else
- switched_to_dl(rq, p);
}

const struct sched_class dl_sched_class = {