thermal: core: Synchronize suspend-prepare and post-suspend actions

After commit 5a5efdaffda5 ("thermal: core: Resume thermal zones
asynchronously") it is theoretically possible that, if a system suspend
starts immediately after a system resume, thermal_zone_device_resume()
spawned by the thermal PM notifier for one of the thermal zones at the
end of the system resume will run after the PM thermal notifier for the
suspend-prepare action.  If that happens, tz->suspended set by the latter
will be reset by the former which may lead to unexpected consequences.

To avoid that race, synchronize thermal_zone_device_resume() with the
suspend-prepare thermal PM notifier with the help of additional bool
field and completion in struct thermal_zone_device.

Note that this also ensures running __thermal_zone_device_update() at
least once for each thermal zone between system resume and the following
system suspend in case it is needed to start thermal mitigation.

Fixes: 5a5efdaffda5 ("thermal: core: Resume thermal zones asynchronously")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 30567b4994551b174e2b96bdfe1189816be115e6..f92529fb0d10e42142ced2c468a2ded89ebc9c38 100644 (file)
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1397,6 +1397,7 @@ thermal_zone_device_register_with_trips(const char *type,
        ida_init(&tz->ida);
        mutex_init(&tz->lock);
        init_completion(&tz->removal);
+       init_completion(&tz->resume);
        id = ida_alloc(&thermal_tz_ida, GFP_KERNEL);
        if (id < 0) {
                result = id;
@@ -1642,6 +1643,9 @@ static void thermal_zone_device_resume(struct work_struct *work)
        thermal_zone_device_init(tz);
        __thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
 
+       complete(&tz->resume);
+       tz->resuming = false;
+
        mutex_unlock(&tz->lock);
 }
 
@@ -1659,6 +1663,20 @@ static int thermal_pm_notify(struct notifier_block *nb,
                list_for_each_entry(tz, &thermal_tz_list, node) {
                        mutex_lock(&tz->lock);
 
+                       if (tz->resuming) {
+                               /*
+                                * thermal_zone_device_resume() queued up for
+                                * this zone has not 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);
+                       }
+
                        tz->suspended = true;
 
                        mutex_unlock(&tz->lock);
@@ -1676,6 +1694,9 @@ static int thermal_pm_notify(struct notifier_block *nb,
 
                        cancel_delayed_work(&tz->poll_queue);
 
+                       reinit_completion(&tz->resume);
+                       tz->resuming = true;
+
                        /*
                         * Replace the work function with the resume one, which
                         * will restore the original work function and schedule

diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
index 20e7b45673d683064209f63ecb0d4cb1b2f5fbdb..66f67e54e0c8dc7701c463b1a8ef994eaeeca154 100644 (file)
--- a/drivers/thermal/thermal_core.h
+++ b/drivers/thermal/thermal_core.h
@@ -55,6 +55,7 @@ struct thermal_governor {
  * @type:      the thermal zone device type
  * @device:    &struct device for this thermal zone
  * @removal:   removal completion
+ * @resume:    resume completion
  * @trip_temp_attrs:   attributes for trip points for sysfs: trip temperature
  * @trip_type_attrs:   attributes for trip points for sysfs: trip type
  * @trip_hyst_attrs:   attributes for trip points for sysfs: trip hysteresis
@@ -89,6 +90,7 @@ struct thermal_governor {
  * @poll_queue:        delayed work for polling
  * @notify_event: Last notification event
  * @suspended: thermal zone suspend indicator
+ * @resuming:  indicates whether or not thermal zone resume is in progress
  * @trips:     array of struct thermal_trip objects
  */
 struct thermal_zone_device {
@@ -96,6 +98,7 @@ struct thermal_zone_device {
        char type[THERMAL_NAME_LENGTH];
        struct device device;
        struct completion removal;
+       struct completion resume;
        struct attribute_group trips_attribute_group;
        struct thermal_attr *trip_temp_attrs;
        struct thermal_attr *trip_type_attrs;
@@ -123,6 +126,7 @@ struct thermal_zone_device {
        struct delayed_work poll_queue;
        enum thermal_notify_event notify_event;
        bool suspended;
+       bool resuming;
 #ifdef CONFIG_THERMAL_DEBUGFS
        struct thermal_debugfs *debugfs;
 #endif