n_tty: Buffer work should not reschedule itself

Although the driver-side input path must update the available
buffer space, it should not reschedule itself. If space is still
available and the flip buffers are not empty, flush_to_ldisc()
will loop again.

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

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 064616542cb5a9f8a5851960dc419dab98b6af59..4bf0fc0843d73bc61cd99d0cc5898177fe0dc39c 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -118,14 +118,14 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
  *     n_tty_set_room  -       receive space
  *     @tty: terminal
  *
- *     Sets tty->receive_room to reflect the currently available space
+ *     Updates tty->receive_room to reflect the currently available space
  *     in the input buffer, and re-schedules the flip buffer work if space
  *     just became available.
  *
  *     Locks: Concurrent update is protected with read_lock
  */
 
-static void n_tty_set_room(struct tty_struct *tty)
+static int set_room(struct tty_struct *tty)
 {
        struct n_tty_data *ldata = tty->disc_data;
        int left;
@@ -155,8 +155,13 @@ static void n_tty_set_room(struct tty_struct *tty)
 
        raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
 
+       return left && !old_left;
+}
+
+static void n_tty_set_room(struct tty_struct *tty)
+{
        /* Did this open up the receive buffer? We may need to flip */
-       if (left && !old_left) {
+       if (set_room(tty)) {
                WARN_RATELIMIT(tty->port->itty == NULL,
                                "scheduling with invalid itty\n");
                /* see if ldisc has been killed - if so, this means that
@@ -1459,7 +1464,7 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                        tty->ops->flush_chars(tty);
        }
 
-       n_tty_set_room(tty);
+       set_room(tty);
 
        if ((!ldata->icanon && (ldata->read_cnt >= ldata->minimum_to_wake)) ||
                L_EXTPROC(tty)) {