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>

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index e8e2775..48b7228 100644 (file)
--- a/drivers/cpuidle/cpuidle.c
+++ b/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());