PM: wakeup: Update after recent wakeup source removal ordering change

After a recent change, wakeup_source_activate() will warn that the given
wakeup source is "unregistered" after its timer has been shut down
in wakeup_source_remove() which may be somewhat confusing, so change
the warning message to say that the wakeup source is "unusable".

Accordingly, rename wakeup_source_not_registered() to
wakeup_source_not_usable() and update the comment in it
to also mention the removal of the wakeup source.

Also restore the comment in wakeup_source_remove() regarding the warning
in wakeup_source_activate() that may trigger after shutting down the
wakeup source timer.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/12788103.O9o76ZdvQC@rafael.j.wysocki

Author: rafaeljw

drivers/base/power/wakeup.c

@@ -189,7 +189,12 @@ static void wakeup_source_remove(struct wakeup_source *ws)
 	if (WARN_ON(!ws))
 		return;
 
+	/*
+	 * After shutting down the timer, wakeup_source_activate() will warn if
+	 * the given wakeup source is passed to it.
+	 */
 	timer_shutdown_sync(&ws->timer);
+
 	raw_spin_lock_irqsave(&events_lock, flags);
 	list_del_rcu(&ws->entry);
 	raw_spin_unlock_irqrestore(&events_lock, flags);
@@ -500,14 +505,14 @@ int device_set_wakeup_enable(struct device *dev, bool enable)
 EXPORT_SYMBOL_GPL(device_set_wakeup_enable);
 
 /**
- * wakeup_source_not_registered - validate the given wakeup source.
+ * wakeup_source_not_usable - validate the given wakeup source.
  * @ws: Wakeup source to be validated.
  */
-static bool wakeup_source_not_registered(struct wakeup_source *ws)
+static bool wakeup_source_not_usable(struct wakeup_source *ws)
 {
 	/*
-	 * Use timer struct to check if the given source is initialized
-	 * by wakeup_source_add.
+	 * Use the timer struct to check if the given wakeup source has been
+	 * initialized by wakeup_source_add() and it is not going away.
 	 */
 	return ws->timer.function != pm_wakeup_timer_fn;
 }
@@ -552,8 +557,7 @@ static void wakeup_source_activate(struct wakeup_source *ws)
 {
 	unsigned int cec;
 
-	if (WARN_ONCE(wakeup_source_not_registered(ws),
-			"unregistered wakeup source\n"))
+	if (WARN_ONCE(wakeup_source_not_usable(ws), "unusable wakeup source\n"))
 		return;
 
 	ws->active = true;