[PATCH 07/18] sched,dl: Convert switched_{from,to}_dl() / prio_changed_dl() to balance callbacks

Peter Zijlstra
2015-06-11T12:54:49Z

[-- Attachment #1: peterz-sched-post_schedule-5.patch --]
[-- Type: text/plain, Size: 3223 bytes --]

Remove the direct {push,pull} balancing operations from
switched_{from,to}_dl() / prio_changed_dl() and use the balance
callback queue.

Again, err on the side of too many reschedules; since too few is a
hard bug while too many is just annoying.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/deadline.c | 45 ++++++++++++++++++++++++---------------------
1 file changed, 24 insertions(+), 21 deletions(-)

--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -213,16 +213,23 @@ static inline bool need_pull_dl_task(str
return dl_task(prev);
}

-static DEFINE_PER_CPU(struct callback_head, dl_balance_head);
+static DEFINE_PER_CPU(struct callback_head, dl_push_head);
+static DEFINE_PER_CPU(struct callback_head, dl_pull_head);

static void push_dl_tasks(struct rq *);
+static void pull_dl_task(struct rq *);

static inline void queue_push_tasks(struct rq *rq)
{
if (!has_pushable_dl_tasks(rq))
return;

- queue_balance_callback(rq, &per_cpu(dl_balance_head, rq->cpu), push_dl_tasks);
+ queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
+}
+
+static inline void queue_pull_task(struct rq *rq)
+{
+ queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
}

static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
@@ -305,6 +312,10 @@ static inline void pull_dl_task(struct r
static inline void queue_push_tasks(struct rq *rq)
{
}
+
+static inline void queue_pull_task(struct rq *rq)
+{
+}
#endif /* CONFIG_SMP */

static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
@@ -1048,8 +1059,6 @@ static void check_preempt_equal_dl(struc
resched_curr(rq);
}

-static void pull_dl_task(struct rq *this_rq);
-
#endif /* CONFIG_SMP */

/*
@@ -1713,7 +1722,7 @@ static void switched_from_dl(struct rq *
if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
return;

- pull_dl_task(rq);
+ queue_pull_task(rq);
}

/*
@@ -1722,21 +1731,16 @@ static void switched_from_dl(struct rq *
*/
static void switched_to_dl(struct rq *rq, struct task_struct *p)
{
- int check_resched = 1;
-
if (task_on_rq_queued(p) && rq->curr != p) {
#ifdef CONFIG_SMP
- if (p->nr_cpus_allowed > 1 && 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) {
- if (dl_task(rq->curr))
- check_preempt_curr_dl(rq, p, 0);
- else
- resched_curr(rq);
- }
+ if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
+ queue_push_tasks(rq);
+#else
+ if (dl_task(rq->curr))
+ check_preempt_curr_dl(rq, p, 0);
+ else
+ resched_curr(rq);
+#endif
}
}

@@ -1756,15 +1760,14 @@ static void prio_changed_dl(struct rq *r
* or lowering its prio, so...
*/
if (!rq->dl.overloaded)
- pull_dl_task(rq);
+ queue_pull_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)
+ if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
resched_curr(rq);
#else
/*