tty: Fix hangup race with TIOCSETD ioctl

The hangup may already have happened; check for that state also.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_ldisc.c

@@ -546,10 +546,8 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 	old_ldisc = tty->ldisc;
 	tty_lock(tty);
 
-	/* FIXME: for testing only */
-	WARN_ON(test_bit(TTY_HUPPED, &tty->flags));
-
-	if (test_bit(TTY_HUPPING, &tty->flags)) {
+	if (test_bit(TTY_HUPPING, &tty->flags) ||
+	    test_bit(TTY_HUPPED, &tty->flags)) {
 		/* We were raced by the hangup method. It will have stomped
 		   the ldisc data and closed the ldisc down */
 		tty_ldisc_enable_pair(tty, o_tty);