[PATCH 7/7] n_tty: Buffer work should not reschedule itself

Peter Hurley
2013-03-06T13:39:16Z

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>
---
drivers/tty/n_tty.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 61a55f4..6f9694d 100644
--- 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
@@ -1475,7 +1480,7 @@ 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)) {
--
1.8.1.2