extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct *tty);
extern void tty_vhangup(struct tty_struct *tty);
extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct *tty);
extern void tty_vhangup(struct tty_struct *tty);