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From:   Chengming Zhou <zhouchengming@bytedance.com>
To:     mingo@redhat.com, peterz@infradead.org, vincent.guittot@linaro.org,
        dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
        vschneid@redhat.com
Cc:     linux-kernel@vger.kernel.org,
        Chengming Zhou <zhouchengming@bytedance.com>
Subject: [PATCH v2 05/10] sched/fair: reset sched_avg last_update_time before set_task_rq()
Date:   Wed, 13 Jul 2022 12:04:25 +0800
Message-Id: <20220713040430.25778-6-zhouchengming@bytedance.com>
In-Reply-To: <20220713040430.25778-1-zhouchengming@bytedance.com>
References: <20220713040430.25778-1-zhouchengming@bytedance.com>
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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@bytedance.com>
---
 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 8992ce5e73d2..171bc22bc142 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11637,12 +11637,12 @@ 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