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tick/nohz: Update idle_exittime on actual idle exit
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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;

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 <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
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yeyunfeng-dev authored and Ingo Molnar committed May 13, 2021
1 parent 3f62431 commit 96c9b90
Showing 1 changed file with 8 additions and 6 deletions.
14 changes: 8 additions & 6 deletions kernel/time/tick-sched.c
Original file line number Diff line number Diff line change
Expand Up @@ -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);
}

Expand Down Expand Up @@ -1194,10 +1192,13 @@ 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;
/*
Expand All @@ -1218,8 +1219,9 @@ 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);
}
}

Expand All @@ -1230,7 +1232,7 @@ 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);
}

/**
Expand Down

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