TTY: pdc_cons, fix open vs pdc_console_tty_driver race

static int __init pdc_console_tty_driver_init(void)

{

	int err;

	struct tty_driver *drv;

	/* Check if the console driver is still registered.

	 * It is unregistered if the pdc console was not selected as the

	printk(KERN_INFO "The PDC console driver is still registered, removing CON_BOOT flag\n");

	pdc_cons.flags &= ~CON_BOOT;

	drv = alloc_tty_driver(1);

	pdc_console_tty_driver = alloc_tty_driver(1);

	if (!drv)

	if (!pdc_console_tty_driver)

		return -ENOMEM;

	drv->driver_name = "pdc_cons";

	drv->name = "ttyB";

	drv->major = MUX_MAJOR;

	drv->minor_start = 0;

	drv->type = TTY_DRIVER_TYPE_SYSTEM;

	drv->init_termios = tty_std_termios;

	drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_RESET_TERMIOS;

	tty_set_operations(drv, &pdc_console_tty_ops);

	err = tty_register_driver(drv);

	pdc_console_tty_driver->driver_name = "pdc_cons";

	pdc_console_tty_driver->name = "ttyB";

	pdc_console_tty_driver->major = MUX_MAJOR;

	pdc_console_tty_driver->minor_start = 0;

	pdc_console_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;

	pdc_console_tty_driver->init_termios = tty_std_termios;

	pdc_console_tty_driver->flags = TTY_DRIVER_REAL_RAW |

		TTY_DRIVER_RESET_TERMIOS;

	tty_set_operations(pdc_console_tty_driver, &pdc_console_tty_ops);

	err = tty_register_driver(pdc_console_tty_driver);

	if (err) {

		printk(KERN_ERR "Unable to register the PDC console TTY driver\n");

		return err;

	}

	pdc_console_tty_driver = drv;

	return 0;

}