tty_ldisc_lock
int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout);
retval = tty_ldisc_lock(tty, 5 * HZ);
retval = tty_ldisc_lock(tty, 5 * HZ);
retval = tty_ldisc_lock(tty, 5 * HZ);
tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT);