[PATCH v4 3/9] sched/fair: reset sched_avg last_update_time before set_task_rq()

[Chengming Zhou]

set_task_rq() -> set_task_rq_fair() will try to synchronize the blocked
task's sched_avg when migrate, which is not needed for already detached
task.

task_change_group_fair() will detached the task sched_avg from prev cfs_rq
first, so reset sched_avg last_update_time before set_task_rq() to avoid that.

Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2c0eb2a4e341..e4c0929a6e71 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11660,12 +11660,12 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
 static void task_change_group_fair(struct task_struct *p)
 {
 	detach_task_cfs_rq(p);
-	set_task_rq(p, task_cpu(p));
 
 #ifdef CONFIG_SMP
 	/* Tell se's cfs_rq has been changed -- migrated */
 	p->se.avg.last_update_time = 0;
 #endif
+	set_task_rq(p, task_cpu(p));
 	attach_task_cfs_rq(p);
 }
 
-- 
2.36.1