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

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2d76c91..b1b105d 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -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);