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timers/nohz: Switch to ONESHOT_STOPPED in the low-res handler when the tick is stopped 

When tick_nohz_stop_tick() stops the tick and high resolution timers are
disabled, then the clock event device is not put into ONESHOT_STOPPED
mode. This can lead to spurious timer interrupts with some clock event
device drivers that don't shut down entirely after firing.

Eliminate these by putting the device into ONESHOT_STOPPED mode at points
where it is not being reprogrammed. When there are no timers active, then
tick_program_event() with KTIME_MAX can be used to stop the device. When
there is a timer active, the device can be stopped at the next tick (any
new timer added by timers will reprogram the tick).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220422141446.915024-1-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2022-04-23 00:14:46 +10:00 committed by Thomas Gleixner
parent ce8abf340e
commit 62c1256d54
1 changed files with 10 additions and 2 deletions
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12
kernel/time/tick-sched.c
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@ -928,6 +928,8 @@ static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
if (unlikely(expires == KTIME_MAX)) {
if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
hrtimer_cancel(&ts->sched_timer);
else
tick_program_event(KTIME_MAX, 1);
return;
}
@ -1364,9 +1366,15 @@ static void tick_nohz_handler(struct clock_event_device *dev)
tick_sched_do_timer(ts, now);
tick_sched_handle(ts, regs);
/* No need to reprogram if we are running tickless */
if (unlikely(ts->tick_stopped))
if (unlikely(ts->tick_stopped)) {
/*
* The clockevent device is not reprogrammed, so change the
* clock event device to ONESHOT_STOPPED to avoid spurious
* interrupts on devices which might not be truly one shot.
*/
tick_program_event(KTIME_MAX, 1);
return;
}
hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);