[patch v7 4/8] sched: fix slept time double counting in enqueue entity

[Alex Shi <alex.shi@intel.com>]

The wakeuped migrated task will __synchronize_entity_decay(se); in
migrate_task_fair, then it needs to set
`se->avg.last_runnable_update -= (-se->avg.decay_count) << 20'
before update_entity_load_avg, in order to avoid slept time is updated
twice for se.avg.load_avg_contrib in both __syncchronize and
update_entity_load_avg.

but if the slept task is waked up from self cpu, it miss the
last_runnable_update before update_entity_load_avg(se, 0, 1), then the
slept time was used twice in both functions.
So we need to remove the double slept time counting.

Signed-off-by: Alex Shi <alex.shi@intel.com>
---
 kernel/sched/fair.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1fc30b9..42c7be0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1570,7 +1570,8 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
 		}
 		wakeup = 0;
 	} else {
-		__synchronize_entity_decay(se);
+		se->avg.last_runnable_update += __synchronize_entity_decay(se)
+							<< 20;
 	}
 
 	/* migrated tasks did not contribute to our blocked load */
-- 
1.7.12