PM: sleep: Simplify dpm_suspended_list walk in dpm_resume()
authorRafael J. Wysocki <rafael.j.wysocki@intel.com>
Mon, 22 Jan 2024 11:22:38 +0000 (12:22 +0100)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Fri, 26 Jan 2024 18:38:36 +0000 (19:38 +0100)
Notice that devices can be moved to dpm_prepared_list before running
their resume callbacks, in analogy with dpm_noirq_resume_devices() and
dpm_resume_early(), because doing so will not affect the final ordering
of that list.

Namely, if a device is the first dpm_suspended_list entry while
dpm_list_mtx is held, it has not been removed so far and it cannot be
removed until dpm_list_mtx is released, so moving it to dpm_prepared_list
at that point is valid.  If it is removed later, while its resume
callback is running, it will be deleted from dpm_prepared_list without
changing the ordering of the other devices in that list.

Accordingly, rearrange the while () loop in dpm_resume() to move
devices to dpm_prepared_list before running their resume callbacks and
implify the locking and device reference counting in it.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
drivers/base/power/main.c

index fadcd0379dc2db7e46fe973ab4429dd659b31d63..10984aa5192bd6af82ff91d8dfbc6ccb5e381a58 100644 (file)
@@ -1017,25 +1017,19 @@ void dpm_resume(pm_message_t state)
 
        while (!list_empty(&dpm_suspended_list)) {
                dev = to_device(dpm_suspended_list.next);
-
-               get_device(dev);
+               list_move_tail(&dev->power.entry, &dpm_prepared_list);
 
                if (!dev->power.async_in_progress) {
+                       get_device(dev);
+
                        mutex_unlock(&dpm_list_mtx);
 
                        device_resume(dev, state, false);
 
+                       put_device(dev);
+
                        mutex_lock(&dpm_list_mtx);
                }
-
-               if (!list_empty(&dev->power.entry))
-                       list_move_tail(&dev->power.entry, &dpm_prepared_list);
-
-               mutex_unlock(&dpm_list_mtx);
-
-               put_device(dev);
-
-               mutex_lock(&dpm_list_mtx);
        }
        mutex_unlock(&dpm_list_mtx);
        async_synchronize_full();