tty: Simplify tty_set_ldisc() exit handling

Perform common exit for both successful and error exit handling
in tty_set_ldisc(). Fixes unlikely possibility of failing to restart
input kworker when switching to the same line discipline (noop case).

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

1 files changed, 13 insertions, 29 deletions

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 7d43ff12f6e2..9ec125046343 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -529,34 +529,21 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
         tty_lock(tty);
         retval = tty_ldisc_lock(tty, 5 * HZ);
-        if (retval) {
-                tty_ldisc_put(new_ldisc);
-                tty_unlock(tty);
-                return retval;
-        }
+        if (retval)
+                goto err;
 
-        /*
-         *      Check the no-op case
-         */
+        /* Check the no-op case */
+        if (tty->ldisc->ops->num == ldisc)
+                goto out;
 
-        if (tty->ldisc->ops->num == ldisc) {
-                tty_ldisc_unlock(tty);
-                tty_ldisc_put(new_ldisc);
-                tty_unlock(tty);
-                return 0;
+        if (test_bit(TTY_HUPPED, &tty->flags)) {
+                /* We were raced by hangup */
+                retval = -EIO;
+                goto out;
         }
 
         old_ldisc = tty->ldisc;
 
-        if (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_unlock(tty);
-                tty_ldisc_put(new_ldisc);
-                tty_unlock(tty);
-                return -EIO;
-        }
-
         /* Shutdown the old discipline. */
         tty_ldisc_close(tty, old_ldisc);
 
@@ -582,18 +569,15 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
            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);
-
-        /*
-         *      Allow ldisc referencing to occur again
-         */
+        new_ldisc = old_ldisc;
+out:
         tty_ldisc_unlock(tty);
 
         /* Restart the work queue in case no characters kick it off. Safe if
            already running */
         tty_buffer_restart_work(tty->port);
-
+err:
+        tty_ldisc_put(new_ldisc);       /* drop the extra reference */
         tty_unlock(tty);
         return retval;
 }