sched/fair: Have task_move_group_fair() also detach entity load from the old runqueue

Since we attach the entity load to the new runqueue, we should also
detatch the entity load from the old runqueue, otherwise load can
accumulate.
Signed-off-by: NByungchul Park <byungchul.park@lge.com>
[ Rewrote the changelog. ]
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: yuyang.du@intel.com
Link: http://lkml.kernel.org/r/1440069720-27038-4-git-send-email-byungchul.park@lge.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

kernel/sched/fair.c

@@ -8037,8 +8037,12 @@ static void task_move_group_fair(struct task_struct *p, int queued)
 	if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
 		queued = 1;
 
+	cfs_rq = cfs_rq_of(se);
 	if (!queued)
-		se->vruntime -= cfs_rq_of(se)->min_vruntime;
+		se->vruntime -= cfs_rq->min_vruntime;
+
+	/* Synchronize task with its prev cfs_rq */
+	detach_entity_load_avg(cfs_rq, se);
 	set_task_rq(p, task_cpu(p));
 	se->depth = se->parent ? se->parent->depth + 1 : 0;
 	cfs_rq = cfs_rq_of(se);