thermal: core: Add and use a reverse thermal zone guard

Add a guard for unlocking a locked thermal zone temporarily and use it
in thermal_zone_pm_prepare().

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <[email protected]>
Link: https://patch.msgid.link/[email protected]
Reviewed-by: Lukasz Luba <[email protected]>

Author: rafaeljw

drivers/thermal/thermal_core.c

@@ -1711,11 +1711,9 @@ static void thermal_zone_pm_prepare(struct thermal_zone_device *tz)
 		 * acquired the lock yet, so release it to let the function run
 		 * and wait util it has done the work.
 		 */
-		mutex_unlock(&tz->lock);
-
-		wait_for_completion(&tz->resume);
-
-		mutex_lock(&tz->lock);
+		scoped_guard(thermal_zone_reverse, tz) {
+			wait_for_completion(&tz->resume);
+		}
 	}
 
 	tz->state |= TZ_STATE_FLAG_SUSPENDED;

drivers/thermal/thermal_core.h

@@ -150,6 +150,9 @@ struct thermal_zone_device {
 DEFINE_GUARD(thermal_zone, struct thermal_zone_device *, mutex_lock(&_T->lock),
 	     mutex_unlock(&_T->lock))
 
+DEFINE_GUARD(thermal_zone_reverse, struct thermal_zone_device *,
+	     mutex_unlock(&_T->lock), mutex_lock(&_T->lock))
+
 /* Initial thermal zone temperature. */
 #define THERMAL_TEMP_INIT	INT_MIN