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

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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@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Wang YanQing 2013-05-09 14:16:47 +08:00 committed by Greg Kroah-Hartman
parent 421b40a628
commit dab73b4eb9
1 changed files with 8 additions and 0 deletions
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8
drivers/tty/n_tty.c
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@ -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);