A small set of fixes for the timers core:

- Fix the warning condition in __run_timers() which does not take into
     account, that a CPU base (especially the deferrable base) has never a
     timer armed on it and therefore the next_expiry value can become stale.
 
   - Replace a WARN_ON() in the NOHZ code with a WARN_ON_ONCE() to prevent
     endless spam in dmesg.
 
   - Remove the double star from a comment which is not meant to be in
     kernel-doc format.
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAmJb44gTHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYoXptD/4tKI9W4q0CAZnXw/G9cJdUK2u2VQGb
 QfB0DMABuDLMlHUSO92T49IcfjQUR7hz36kHXY0OxwALaEB8ftap6yZLfI1864mZ
 RFatWcTl71ZYY0SSio0rMnbDawTeN9N69WLPR+A6fDH0ahBqTwpeJoa1zj5w99LF
 kFoEtI5vEBtf+m94PljBTclxOKTXmRRCzEZRpJ6L4Ze9SHR7aMKtBgp84M7a3IAw
 IzXq0Kw0MRIm4P26uOpsVzi2KOq6+F1O1zy4L8cHVeU+Y6HC1qWLPXsyhipb0liE
 6STFs1L7ANX+dpMW8kmorXc3RcN4xCuCY4Sb17W6Hqiq3syQ+Ho2G0CTheL0yOpM
 GVqf7SVes3EGAJwWyKaFmhpgWGKcS93p18XGUrf5V+rVIU+ggQcc2vM9E8FiM03d
 TA6T9+1u0TvtPlmd/KQ3OPLMEtu6/3R0fOLEXnv+Cb/PYIYMvPpb9cu6LjJkNqGv
 6R+3dWORI7mYLZD+vS3Y5mrmB5OECGXTPNJ+aBr46PfdvSVLxvmOhFlNR7eQKHZ8
 wFwOC6n4wkD5Y1VOVGEn0GVGWVkZXdlQzZOQGqBhJPjsfPfOaGacyLqCcsZH4V6w
 kitKI8z7A7evLozZMQqKZskwLG1BTQ13YeElb5jJMpG3aTG7lSmPk+iGgLFMDWkc
 Z2k4YD0Uw+92Tw==
 =SffK
 -----END PGP SIGNATURE-----

Merge tag 'timers-urgent-2022-04-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fixes from Thomas Gleixner:
 "A small set of fixes for the timers core:

   - Fix the warning condition in __run_timers() which does not take
     into account that a CPU base (especially the deferrable base) never
     has a timer armed on it and therefore the next_expiry value can
     become stale.

   - Replace a WARN_ON() in the NOHZ code with a WARN_ON_ONCE() to
     prevent endless spam in dmesg.

   - Remove the double star from a comment which is not meant to be in
     kernel-doc format"

* tag 'timers-urgent-2022-04-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tick/sched: Fix non-kernel-doc comment
  tick/nohz: Use WARN_ON_ONCE() to prevent console saturation
  timers: Fix warning condition in __run_timers()

kernel/time/tick-sched.c

@@ -188,7 +188,7 @@ static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
 	 */
 	if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) {
 #ifdef CONFIG_NO_HZ_FULL
-		WARN_ON(tick_nohz_full_running);
+		WARN_ON_ONCE(tick_nohz_full_running);
 #endif
 		tick_do_timer_cpu = cpu;
 	}
@@ -1538,7 +1538,7 @@ void tick_cancel_sched_timer(int cpu)
 }
 #endif
 
-/**
+/*
  * Async notification about clocksource changes
  */
 void tick_clock_notify(void)
@@ -1559,7 +1559,7 @@ void tick_oneshot_notify(void)
 	set_bit(0, &ts->check_clocks);
 }
 
-/**
+/*
  * Check, if a change happened, which makes oneshot possible.
  *
  * Called cyclic from the hrtimer softirq (driven by the timer

kernel/time/timer.c

@@ -1722,11 +1722,14 @@ static inline void __run_timers(struct timer_base *base)
 	       time_after_eq(jiffies, base->next_expiry)) {
 		levels = collect_expired_timers(base, heads);
 		/*
-		 * The only possible reason for not finding any expired
-		 * timer at this clk is that all matching timers have been
-		 * dequeued.
+		 * The two possible reasons for not finding any expired
+		 * timer at this clk are that all matching timers have been
+		 * dequeued or no timer has been queued since
+		 * base::next_expiry was set to base::clk +
+		 * NEXT_TIMER_MAX_DELTA.
 		 */
-		WARN_ON_ONCE(!levels && !base->next_expiry_recalc);
+		WARN_ON_ONCE(!levels && !base->next_expiry_recalc
+			     && base->timers_pending);
 		base->clk++;
 		base->next_expiry = __next_timer_interrupt(base);