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Subject[PATCH 4/8] tick/nohz: Update idle_exittime on actual idle exit
Date
From: Yunfeng Ye <yeyunfeng@huawei.com>

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;

It's thus overwritten by mistake on nohz_full tick restart. Move the
update to the appropriate idle exit path instead.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Cc: Yunfeng Ye <yeyunfeng@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
kernel/time/tick-sched.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 31efd55ed302..ffc13b9dfbe3 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -921,8 +921,6 @@ 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);
}

@@ -1190,10 +1188,13 @@ unsigned long tick_nohz_get_idle_calls(void)
return ts->idle_calls;
}

-static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
+static void tick_nohz_account_idle_time(struct tick_sched *ts,
+ ktime_t now)
{
unsigned long ticks;

+ ts->idle_exittime = now;
+
if (vtime_accounting_enabled_this_cpu())
return;
/*
@@ -1214,8 +1215,9 @@ void tick_nohz_idle_restart_tick(void)
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);

if (ts->tick_stopped) {
- tick_nohz_restart_sched_tick(ts, ktime_get());
- tick_nohz_account_idle_ticks(ts);
+ ktime_t now = ktime_get();
+ tick_nohz_restart_sched_tick(ts, now);
+ tick_nohz_account_idle_time(ts, now);
}
}

@@ -1226,7 +1228,7 @@ static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
else
tick_nohz_restart_sched_tick(ts, now);

- tick_nohz_account_idle_ticks(ts);
+ tick_nohz_account_idle_time(ts, now);
}

/**
--
2.25.1
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