sched: fix sched_slice()

Impact: fix bad-interactivity buglet

Fix sched_slice() to emit a sane result whether a task is currently
enqueued or not.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Tested-by: Jayson King <dev@jaysonking.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

 kernel/sched_fair.c |   30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

kernel/sched_fair.c

@@ -385,20 +385,6 @@ int sched_nr_latency_handler(struct ctl_table *table, int write,
 }
 #endif
 
-/*
- * delta *= P[w / rw]
- */
-static inline unsigned long
-calc_delta_weight(unsigned long delta, struct sched_entity *se)
-{
-	for_each_sched_entity(se) {
-		delta = calc_delta_mine(delta,
-				se->load.weight, &cfs_rq_of(se)->load);
-	}
-
-	return delta;
-}
-
 /*
  * delta /= w
  */
@@ -440,12 +426,20 @@ static u64 __sched_period(unsigned long nr_running)
  */
 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	unsigned long nr_running = cfs_rq->nr_running;
+	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
 
-	if (unlikely(!se->on_rq))
-		nr_running++;
+	for_each_sched_entity(se) {
+		struct load_weight *load = &cfs_rq->load;
 
-	return calc_delta_weight(__sched_period(nr_running), se);
+		if (unlikely(!se->on_rq)) {
+			struct load_weight lw = cfs_rq->load;
+
+			update_load_add(&lw, se->load.weight);
+			load = &lw;
+		}
+		slice = calc_delta_mine(slice, se->load.weight, load);
+	}
+	return slice;
 }
 
 /*