[BUG?] tty doesn't handle ^D at cooked/non-cooked switching corner case

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Hi tty expert,

Recently, ruby (scripting program language) developing group found
that linux doesn't handle ^D properly at cooked/non-cooked switching
corner case.

They (and I) think it isn't typical case, but scripting language vm
shouldn't hang up although script user write any crap and strange code.

They create following patch. is it right way?



reproduce way
--------------
1. run tty_test.sh (see below)
2. input any key before output "cooked"
3. input ^D, but do nothing


tty_test.sh
--------------
#!/bin/sh

exec 3<&0
cat <&3 &
pid=$!
stty -icanon
echo raw
sleep 1
stty icanon
echo cooked
wait $pid

---
 drivers/char/n_tty.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: b/drivers/char/n_tty.c
===================================================================
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1893,7 +1893,7 @@ do_it_again:
 			check_unthrottle(tty);
 		}
 
-		if (b - buf >= minimum)
+		if (b - buf >= (tty->icanon ? 0 : minimum))
 			break;
 		if (time)
 			timeout = time;