tty: Clarify multiple-references comment in TIOCSETD ioctl

Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_ldisc.c

@@ -570,13 +570,15 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 		tty_ldisc_restore(tty, old_ldisc);
 	}
 
-	/* At this point we hold a reference to the new ldisc and a
-	   a reference to the old ldisc. If we ended up flipping back
-	   to the existing ldisc we have two references to it */
-
 	if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc)
 		tty->ops->set_ldisc(tty);
 
+	/* At this point we hold a reference to the new ldisc and a
+	   reference to the old ldisc, or we hold two references to
+	   the old ldisc (if it was restored as part of error cleanup
+	   above). In either case, releasing a single reference from
+	   the old ldisc is correct. */
+
 	tty_ldisc_put(old_ldisc);
 
 	/*