thermal: core: Mark thermal zones as exiting before unregistration

In analogy with a previous change in the thermal zone registration code
path, to ensure that __thermal_zone_device_update() will return early
for thermal zones that are going away, introduce a thermal zone state
flag representing the "exit" state and set it while deleting the thermal
zone from thermal_tz_list.

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

@@ -1621,7 +1621,10 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 	}
 
 	mutex_lock(&tz->lock);
+
+	tz->state |= TZ_STATE_FLAG_EXIT;
 	list_del(&tz->node);
+
 	mutex_unlock(&tz->lock);
 
 	/* Unbind all cdevs associated with 'this' thermal zone */

drivers/thermal/thermal_core.h

@@ -65,6 +65,7 @@ struct thermal_governor {
 #define	TZ_STATE_FLAG_SUSPENDED	BIT(0)
 #define	TZ_STATE_FLAG_RESUMING	BIT(1)
 #define	TZ_STATE_FLAG_INIT	BIT(2)
+#define	TZ_STATE_FLAG_EXIT	BIT(3)
 
 #define TZ_STATE_READY		0