Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull UP timer fix from Thomas Gleixner:
 "Work around the for_each_cpu() oddity on UP kernels in the tick
  broadcast code which causes boot failures because the CPU0 bit is
  always reported as set independent of the cpumask content"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tick/broadcast: Use for_each_cpu() specially on UP kernels

Author: torvalds

kernel/time/tick-broadcast.c

@@ -612,6 +612,14 @@ static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 	now = ktime_get();
 	/* Find all expired events */
 	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
+		/*
+		 * Required for !SMP because for_each_cpu() reports
+		 * unconditionally CPU0 as set on UP kernels.
+		 */
+		if (!IS_ENABLED(CONFIG_SMP) &&
+		    cpumask_empty(tick_broadcast_oneshot_mask))
+			break;
+
 		td = &per_cpu(tick_cpu_device, cpu);
 		if (td->evtdev->next_event <= now) {
 			cpumask_set_cpu(cpu, tmpmask);