suspend-to-idle: Prevent RCU from complaining about tick_freeze()

Put tick_freeze() under RCU_NONIDLE() to prevent RCU from complaining
about suspicious RCU usage in idle by trace_suspend_resume() called
from there.

While at it, fix a comment related to another usage of RCU_NONIDLE()
in enter_freeze_proper().
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

drivers/cpuidle/cpuidle.c

@@ -112,7 +112,12 @@ int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 static void enter_freeze_proper(struct cpuidle_driver *drv,
 				struct cpuidle_device *dev, int index)
 {
-	tick_freeze();
+	/*
+	 * trace_suspend_resume() called by tick_freeze() for the last CPU
+	 * executing it contains RCU usage regarded as invalid in the idle
+	 * context, so tell RCU about that.
+	 */
+	RCU_NONIDLE(tick_freeze());
 	/*
 	 * The state used here cannot be a "coupled" one, because the "coupled"
 	 * cpuidle mechanism enables interrupts and doing that with timekeeping
@@ -122,7 +127,7 @@ static void enter_freeze_proper(struct cpuidle_driver *drv,
 	WARN_ON(!irqs_disabled());
 	/*
 	 * timekeeping_resume() that will be called by tick_unfreeze() for the
-	 * last CPU executing it calls functions containing RCU read-side
+	 * first CPU executing it calls functions containing RCU read-side
 	 * critical sections, so tell RCU about that.
 	 */
 	RCU_NONIDLE(tick_unfreeze());