ACPI / Battery: Resolve the race condition in the sysfs_remove_battery()

Use battery->lock in sysfs_remove_battery() to make
checking, removing, and clearing bat.dev atomic.
This is necessary because sysfs_remove_battery() may
be invoked concurrently from different paths.

    https://bugzilla.kernel.org/show_bug.cgi?id=35642

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/battery.c

@@ -573,11 +573,16 @@ static int sysfs_add_battery(struct acpi_battery *battery)
 
 static void sysfs_remove_battery(struct acpi_battery *battery)
 {
-	if (!battery->bat.dev)
+	mutex_lock(&battery->lock);
+	if (!battery->bat.dev) {
+		mutex_unlock(&battery->lock);
 		return;
+	}
+
 	device_remove_file(battery->bat.dev, &alarm_attr);
 	power_supply_unregister(&battery->bat);
 	battery->bat.dev = NULL;
+	mutex_unlock(&battery->lock);
 }
 
 /*