--- x/drivers/bluetooth/hci_serdev.c
+++ y/drivers/bluetooth/hci_serdev.c
@@ -395,7 +395,10 @@ void hci_uart_unregister_device(struct h
 	hu->proto->close(hu);
 
 	if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) {
+		percpu_down_write(&hu->proto_lock);
 		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
+		percpu_up_write(&hu->proto_lock);
+
 		serdev_device_close(hu->serdev);
 	}
 }