From: Ramesh Thomas <ramesh.thomas@xxxxxxxxx>
After all conditions to enter nohz_full state are met, if a timer event
is detected in the next period, nohz_full entry is aborted in
tick_nohz_next_event(). In the failure condition, this scenario keeps
repeating. This has been reproduced in preempt_rt kernel, however it may
not be limited to it.
Not bailing out if CONFIG_NO_HZ_FULL is defined, fixes the issue. Since
in NO_HZ_FULL mode, idle state is not entered at tick stoppage, the
pending timer event can be handled where the next timer is programmed in
tick_nohz_stop_tick(). This also simplifies the logic by keeping a
common path to handle the entry/exit of nohz_full state, whether the
tick was already stopped or not.
(The entire check for the presence of a timer event in the next period
can possibly be skipped for NO_HZ_FULL)
Signed-off-by: Ramesh Thomas <ramesh.thomas@xxxxxxxxx>
---
kernel/time/tick-sched.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 308a98c28ee8..3798dbc5f082 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -739,10 +739,12 @@ static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
* We've not stopped the tick yet, and there's a timer in the
* next period, so no point in stopping it either, bail.
*/
+#ifndef CONFIG_NO_HZ_FULL
if (!ts->tick_stopped) {
ts->timer_expires = 0;
- goto out;
+ return 0;
}
+#endif
}
/*
@@ -763,7 +765,6 @@ static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
ts->timer_expires = min_t(u64, expires, next_tick);
-out:
return ts->timer_expires;
}
--
2.26.2
