[PATCH] (*revised*) Fix IXANY and restart after signal (e.g. ctrl-C) in n_tty line discipline

[Joe Peterson <joe@skyrush.com>]

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Here is a revised version of my patch, currently in the -mm kernel as
"fix-ixany-and-restart-after-signal-eg-ctrl-c-in-n_tty-line-discipline".
It fixes a couple of issues with ttys in the stopped state.  See patch
below for more details.

This patch should *replace* the old version of the patch.  It is
cleaner, and its behavior better matches that of other Unix platforms.
It also avoids needless/redundant calls to start_tty() when ctrl-S or
ctrl-Q are hit.

							-Joe

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Fix two N_TTY line discipline issues related to resuming a stopped TTY
(typically done with ctrl-S):

1) Fix handling of character that resumes a stopped TTY (with IXANY)

With "stty ixany", the TTY line discipline would lose the first character
after the stop, so typing, for example, "hi^Sthere" resulted in "hihere"
(the 't' would cause the resume after ^S, but it would then be thrown away
rather than processed as an input character).  This was inconsistent with
the behavior of other Unix systems.

2) Fix interrupt signal (e.g. ctrl-C) behavior in stopped TTYs

With "stty -ixany" (often the default), interrupt signals were ignored
in a stopped TTY until the TTY was resumed with the start char (typically
ctrl-Q), which was inconsistent with the behavior of other Unix systems.

Signed-off-by: Joe Peterson <joe@skyrush.com>
---

diff -puN drivers/char/n_tty.c~fix-ixany-and-restart-after-signal-eg-ctrl-c-in-n_tty-line-discipline drivers/char/n_tty.c
--- a/drivers/char/n_tty.c~fix-ixany-and-restart-after-signal-eg-ctrl-c-in-n_tty-line-discipline	2007-12-20 11:35:05.000000000 -0700
+++ a/drivers/char/n_tty.c	2007-12-20 11:35:36.000000000 -0700
@@ -695,17 +695,16 @@
 		return;
 	}
 	
-	if (tty->stopped && !tty->flow_stopped &&
-	    I_IXON(tty) && I_IXANY(tty)) {
-		start_tty(tty);
-		return;
-	}
-	
 	if (I_ISTRIP(tty))
 		c &= 0x7f;
 	if (I_IUCLC(tty) && L_IEXTEN(tty))
 		c=tolower(c);
 
+	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
+	    ((I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty)) ||
+	     c == INTR_CHAR(tty) || c == QUIT_CHAR(tty)))
+		start_tty(tty);
+
 	if (tty->closing) {
 		if (I_IXON(tty)) {
 			if (c == START_CHAR(tty))