sched, dl: Convert switched_{from, to}_dl() / prio_changed_dl() to balance callbacks

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>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: oleg@redhat.com
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124742.968262663@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 079c09251e90ae2cf5894d393a6b263bfdd5ac20..69d9f509a582611631480aa890fce73493cbfeb7 100644 (file)
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -213,16 +213,23 @@ static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
        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 rq *rq)
 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);
@@ -1040,8 +1051,6 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
        resched_curr(rq);
 }
 
-static void pull_dl_task(struct rq *this_rq);
-
 #endif /* CONFIG_SMP */
 
 /*
@@ -1705,7 +1714,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
        if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
                return;
 
-       pull_dl_task(rq);
+       queue_pull_task(rq);
 }
 
 /*
@@ -1714,21 +1723,16 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
  */
 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
        }
 }
 
@@ -1748,15 +1752,14 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
                 * 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
                /*