From 0a44ab41eb833d07e3ec807d87151c7164d4f075 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Fri, 22 Jun 2012 16:40:20 +0100 Subject: tty: note race we need to fix 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 Signed-off-by: Greg Kroah-Hartman 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) -- cgit v0.10.2