clockevents: fix device replacement

When a device is replaced by a better rated device, then the broadcast
mode needs to be evaluated again. When the new device has no requirement
for broadcasting, then the broadcast bits for the CPU must be cleared.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/time/tick-broadcast.c

@@ -31,6 +31,12 @@ struct tick_device tick_broadcast_device;
 static cpumask_t tick_broadcast_mask;
 static DEFINE_SPINLOCK(tick_broadcast_lock);
 
+#ifdef CONFIG_TICK_ONESHOT
+static void tick_broadcast_clear_oneshot(int cpu);
+#else
+static inline void tick_broadcast_clear_oneshot(int cpu) { }
+#endif
+
 /*
  * Debugging: see timer_list.c
  */
@@ -99,8 +105,19 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 		cpu_set(cpu, tick_broadcast_mask);
 		tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
 		ret = 1;
-	}
+	} else {
+		/*
+		 * When the new device is not affected by the stop
+		 * feature and the cpu is marked in the broadcast mask
+		 * then clear the broadcast bit.
+		 */
+		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
+			int cpu = smp_processor_id();
 
+			cpu_clear(cpu, tick_broadcast_mask);
+			tick_broadcast_clear_oneshot(cpu);
+		}
+	}
 	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 	return ret;
 }
@@ -487,6 +504,16 @@ void tick_broadcast_oneshot_control(unsigned long reason)
 	spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }
 
+/*
+ * Reset the one shot broadcast for a cpu
+ *
+ * Called with tick_broadcast_lock held
+ */
+static void tick_broadcast_clear_oneshot(int cpu)
+{
+	cpu_clear(cpu, tick_broadcast_oneshot_mask);
+}
+
 /**
  * tick_broadcast_setup_highres - setup the broadcast device for highres
  */