[PATCH 03/12] tty: note race we need to fix

Alan Cox
2012-06-22T15:24:34Z

This was identified by Vincent Pillet with a high speed interface that uses
low latency mode. In the low latency case we have a tiny race but it can
be hit.

Signed-off-by: Alan Cox <alan@linux.intel.com>
---

drivers/tty/n_tty.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index ee1c268..4f34491 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1432,6 +1432,12 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
*/
if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
tty_throttle(tty);
+
+ /* FIXME: there is a tiny race here if the receive room check runs
+ before the other work executes and empties the buffer (upping
+ the receiving room and unthrottling. We then throttle and get
+ stuck. This has been observed and traced down by Vincent Pillet/
+ We need to address this when we sort out out the rx path locking */
}

int is_ignored(int sig)