[PATCH 07/14] sched,dl: Convert switched_{from,to}_dl() / prio_changed_dl() to balance callbacks

[Peter Zijlstra]

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) <pet...@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
                /*


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