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Subject: [PATCH] tick/nohz: Make the idle_exittime update correctly
From:   Yunfeng Ye <yeyunfeng@huawei.com>
To:     <fweisbec@gmail.com>, <tglx@linutronix.de>, <mingo@kernel.org>,
        <linux-kernel@vger.kernel.org>
CC:     Shiyuan Hu <hushiyuan@huawei.com>,
        Hewenliang <hewenliang4@huawei.com>
References: <2e194669-c074-069c-4fda-ad5bc313a611@huawei.com>
Message-ID: <bc6f830d-21da-b334-9dfd-54dcf2d4f7a0@huawei.com>
Date:   Tue, 15 Dec 2020 20:06:34 +0800
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The idle_exittime field of tick_sched is used to record the time when
the idle state was left. but currently the idle_exittime is updated in
the function tick_nohz_restart_sched_tick(), which is not always in idle
state when nohz_full is configured.

  tick_irq_exit
    tick_nohz_irq_exit
      tick_nohz_full_update_tick
        tick_nohz_restart_sched_tick
          ts->idle_exittime = now;

So move to tick_nohz_stop_idle() to make the idle_exittime update
correctly.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
---
 kernel/time/tick-sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 749ec2a583de..be2e5d772d50 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -591,6 +591,7 @@ static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
 {
 	update_ts_time_stats(smp_processor_id(), ts, now, NULL);
 	ts->idle_active = 0;
+	ts->idle_exittime = now;

 	sched_clock_idle_wakeup_event();
 }
@@ -901,7 +902,6 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
 	 * Cancel the scheduled timer and restore the tick
 	 */
 	ts->tick_stopped  = 0;
-	ts->idle_exittime = now;

 	tick_nohz_restart(ts, now);
 }
-- 
2.18.4