UPF_DEAD 1788 drivers/tty/serial/serial_core.c if (!uport || uport->flags & UPF_DEAD) UPF_DEAD 2872 drivers/tty/serial/serial_core.c uport->flags &= ~UPF_DEAD; UPF_DEAD 2917 drivers/tty/serial/serial_core.c uport->flags |= UPF_DEAD;