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

commit 9916e214998a4a363b152b637245e5c958067350 upstream.

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>
[Conflicts: kernel/sched/deadline.c]
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
[bwh: Backported to 3.16:
 - The check_resched / !CONFIG_SMP case in switched_to_dl() is different
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 12c8927369768514f9172ef093c4fbc3a2f4b4af..ab8b917ce8f6b7b1a6fba87b161b1ab003dc2947 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);
 }
 
 #else
@@ -259,6 +266,10 @@ 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);
@@ -956,8 +967,6 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
        resched_task(rq->curr);
 }
 
-static void pull_dl_task(struct rq *this_rq);
-
 #endif /* CONFIG_SMP */
 
 /*
@@ -1562,7 +1571,7 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
         * from an overloaded cpu, if any.
         */
        if (!rq->dl.dl_nr_running)
-               pull_dl_task(rq);
+               queue_pull_task(rq);
 #endif
 }
 
@@ -1572,8 +1581,6 @@ 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 p is throttled, don't consider the possibility
         * of preempting rq->curr, the check will be done right
@@ -1584,12 +1591,12 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
 
        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))
+               if (rq->dl.overloaded)
+                       queue_push_tasks(rq);
+#else
+               if (task_has_dl_policy(rq->curr))
                        check_preempt_curr_dl(rq, p, 0);
+#endif /* CONFIG_SMP */
        }
 }
 
@@ -1609,15 +1616,14 @@ 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_task(p);
 #else
                /*