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.
But after search the emacs's startup codes, I find they use TCXONC
to workaround this situation:
/* This code added to insure that, if flow-control is not to be used,
we have an unlocked terminal at the start. */
if (!tty_out->flow_control) ioctl (fileno (tty_out->input), TCXONC, 1);
ioctl (fileno (tty_out->input), TCXONC, 1);
But this workaround never work due the kernel's current code.
This patch fix it.
Below is the ChangeLog introduce the tty->flow_stopped flag:
Thu Nov 21 10:05:22 1996 Theodre Ts'o <ty...@localhost.mit.edu>
* tty_ioctl.c (tty_wait_until_sent): Always check the driver
wait_until_ready routine, even if there are no characters
in the xmit buffer. (There may be charactes in the device
FIFO.)
(n_tty_ioctl): Add new flag tty->flow_stopped which
indicates whether the tty is stopped due to a request by
the TCXONC ioctl (used by tcflow). If so, don't let an
incoming XOFF character restart the tty. The tty can only
be restarted by another TCXONC request.
So I think this patch make TCXONC can restart tty which stopped by
STOP_CHAR don't break the original meaning.
This patch will fix some 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 <udkni...@gmail.com>
---
drivers/tty/tty_ioctl.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index e4455e0..42e08e5 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -1129,11 +1129,12 @@ int n_tty_ioctl_helper(struct tty_struct *tty, struct
file *file,
case TCOOFF:
if (!tty->flow_stopped) {
tty->flow_stopped = 1;
- stop_tty(tty);
+ if (!tty->stopped)
+ stop_tty(tty);
}
break;
case TCOON:
- if (tty->flow_stopped) {
+ if (tty->flow_stopped || tty->stopped) {
tty->flow_stopped = 0;
start_tty(tty);
}
--
1.7.12.4.dirty
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
