From dab73b4eb9ef924a2b90dab84e539076d82b256f Mon Sep 17 00:00:00 2001 From: Wang YanQing Date: Thu, 9 May 2013 14:16:47 +0800 Subject: [PATCH] TTY: Fix tty miss restart after we turn off flow-control I meet emacs hang in start if I do the operation below: 1: echo 3 > /proc/sys/vm/drop_caches 2: emacs BigFile 3: Press CTRL-S follow 2 immediately Then emacs hang on, CTRL-Q can't resume, the terminal hang on, you can do nothing with this terminal except close it. The reason is before emacs takeover control the tty, we use CTRL-S to XOFF it. Then when emacs takeover the control, it may don't use the flow-control, so emacs hang. This patch fix it. This patch will fix a kind of strange tty relation hang problem, I believe I meet it with vim in ssh, and also see below bug report: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=465823 Signed-off-by: Wang YanQing Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index d655416087b7..6c7fe90ad72d 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1573,6 +1573,14 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) ldata->real_raw = 0; } n_tty_set_room(tty); + /* + * Fix tty hang when I_IXON(tty) is cleared, but the tty + * been stopped by STOP_CHAR(tty) before it. + */ + if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) { + start_tty(tty); + } + /* The termios change make the tty ready for I/O */ wake_up_interruptible(&tty->write_wait); wake_up_interruptible(&tty->read_wait);