[PATCH v3 4/5] tick/nohz: Reset got_idle_tick when entering dynticks idle

[Marco Crivellari <marco.crivellari@suse.com>]

A tick firing after the last tick_nohz_idle_got_tick() and before
tick_nohz_idle_exit() leaves got_idle_tick set, and the next
cpuidle_idle_call() then assumes that a later dynticks idle period was
ended by the tick. Now that the CPU leaves dynticks idle before polling,
this can also happen within a single idle trip when it switches between
cpuidle and polling, e.g. when it polls because the tick broadcast has
expired.

Reset got_idle_tick when entering dynticks idle, so that it only reports
the ticks of the current period.

Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 kernel/time/tick-sched.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index b4149f40b5f1..fb47d5dfbf4e 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1237,6 +1237,8 @@ void tick_nohz_idle_enter(void)
 	if (tick_sched_flag_test(ts, TS_FLAG_INIDLE))
 		return;
 
+	/* Only report the ticks of this dynticks idle period */
+	ts->got_idle_tick = 0;
 	WARN_ON_ONCE(ts->timer_expires_base);
 	tick_sched_flag_set(ts, TS_FLAG_INIDLE);
 	ts->idle_entrytime = ktime_get();
-- 
2.56.0