[PATCH 03/12] tty: Note n_tty race
From: Alan Cox <hidden>
Date: 2012-06-27 11:05:28
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
From: Alan Cox <redacted> 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 <redacted> --- 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)