From eb2f61c4df7ac117fdf58ad75905e97fff3a0cc1 Mon Sep 17 00:00:00 2001
From: christos <christos@NetBSD.org>
Date: Sun, 12 Aug 2012 14:45:44 +0000
Subject: [PATCH] PR/46780: Dennis Ferguson: Take the easy way out and return
 EBUSY when changing the queue size if the output queue is not empty. Other
 solutions seemed too complex/fragile.

---
 sys/kern/tty.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index e47c7a7a81ab..18b4233c5af0 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: tty.c,v 1.250 2012/03/12 18:27:08 christos Exp $	*/
+/*	$NetBSD: tty.c,v 1.251 2012/08/12 14:45:44 christos Exp $	*/
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -63,7 +63,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tty.c,v 1.250 2012/03/12 18:27:08 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tty.c,v 1.251 2012/08/12 14:45:44 christos Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -224,12 +224,15 @@ tty_get_qsize(int *qsize, int newsize)
 	return 0;
 }
 
-static void
+static int
 tty_set_qsize(struct tty *tp, int newsize)
 {
 	struct clist rawq, canq, outq;
 	struct clist orawq, ocanq, ooutq;
 
+	if (outq.c_cc != 0)
+		return EBUSY;
+
 	clalloc(&rawq, newsize, 1);
 	clalloc(&canq, newsize, 1);
 	clalloc(&outq, newsize, 0);
@@ -252,6 +255,8 @@ tty_set_qsize(struct tty *tp, int newsize)
 	clfree(&orawq);
 	clfree(&ocanq);
 	clfree(&ooutq);
+
+	return 0;
 }
 
 static int
@@ -1350,7 +1355,7 @@ ttioctl(struct tty *tp, u_long cmd, void *data, int flag, struct lwp *l)
 	case TIOCSQSIZE:
 		if ((error = tty_get_qsize(&s, *(int *)data)) == 0 &&
 		    s != tp->t_qsize)
-			tty_set_qsize(tp, s);
+			error = tty_set_qsize(tp, s);
 		return error;
 	default:
 		/* We may have to load the compat module for this. */