Patch "TTY: Fix tty miss restart after we turn off flow-control" has been added to the 3.9-stable tree

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This is a note to let you know that I've just added the patch titled

    TTY: Fix tty miss restart after we turn off flow-control

to the 3.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tty-fix-tty-miss-restart-after-we-turn-off-flow-control.patch
and it can be found in the queue-3.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From dab73b4eb9ef924a2b90dab84e539076d82b256f Mon Sep 17 00:00:00 2001
From: Wang YanQing <udknight@xxxxxxxxx>
Date: Thu, 9 May 2013 14:16:47 +0800
Subject: TTY: Fix tty miss restart after we turn off flow-control

From: Wang YanQing <udknight@xxxxxxxxx>

commit dab73b4eb9ef924a2b90dab84e539076d82b256f upstream.

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 <udknight@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/n_tty.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1588,6 +1588,14 @@ static void n_tty_set_termios(struct tty
 			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);


Patches currently in stable-queue which might be from udknight@xxxxxxxxx are

queue-3.9/tty-fix-tty-miss-restart-after-we-turn-off-flow-control.patch
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