[PATCH stable backport] clockevents: Add missing resets of the next_event_forced flag

[Thomas Gleixner]

commit 4096fd0e8eaea13ebe5206700b33f49635ae18e5 upstream.

The prevention mechanism against timer interrupt starvation missed to reset
the next_event_forced flag in a couple of places:

    - When the clock event state changes. That can cause the flag to be
      stale over a shutdown/startup sequence

    - When a non-forced event is armed, which then prevents rearming before
      that event. If that event is far out in the future this will cause
      missed timer interrupts.

    - In the suspend wakeup handler.

That led to stalls which have been reported by several people.

Add the missing resets, which fixes the problems for the reporters.

Fixes: d6e152d905bd ("clockevents: Prevent timer interrupt starvation")
Reported-by: Hanabishi <i.r.e.c.c.a.k.u.n+kernel.org@xxxxxxxxx>
Reported-by: Eric Naim <dnaim@xxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Tested-by: Hanabishi <i.r.e.c.c.a.k.u.n+kernel.org@xxxxxxxxx>
Tested-by: Eric Naim <dnaim@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/68d1e9ac-2780-4be3-8ee3-0788062dd3a4@xxxxxxxxx
Link: https://patch.msgid.link/87340xfeje.ffs@tglx

---
 kernel/time/clockevents.c    |    7 ++++++-
 kernel/time/tick-broadcast.c |    1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -94,6 +94,9 @@ static int __clockevents_switch_state(st
 	if (dev->features & CLOCK_EVT_FEAT_DUMMY)
 		return 0;
 
+	/* On state transitions clear the forced flag unconditionally */
+	dev->next_event_forced = 0;
+
 	/* Transition with new state-specific callbacks */
 	switch (state) {
 	case CLOCK_EVT_STATE_DETACHED:
@@ -332,8 +335,10 @@ int clockevents_program_event(struct clo
 	if (delta > (int64_t)dev->min_delta_ns) {
 		delta = min(delta, (int64_t) dev->max_delta_ns);
 		clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
-		if (!dev->set_next_event((unsigned long) clc, dev))
+		if (!dev->set_next_event((unsigned long) clc, dev)) {
+			dev->next_event_forced = 0;
 			return 0;
+		}
 	}
 
 	if (dev->next_event_forced)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -108,6 +108,7 @@ static struct clock_event_device *tick_g
 
 static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
 {
+	wd->next_event_forced = 0;
 	/*
 	 * If we woke up early and the tick was reprogrammed in the
 	 * meantime then this may be spurious but harmless.