tty: Prevent "read/write wait queue active!" log flooding

commit 494c1eac upstream.

Only print one warning when a task is on the read_wait or write_wait
wait queue at final tty release.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>

drivers/tty/tty_io.c

@@ -1634,6 +1634,7 @@ int tty_release(struct inode *inode, struct file *filp)
 	int	idx;
 	char	buf[64];
 	long	timeout = 0;
+	int	once = 1;
 
 	if (tty_paranoia_check(tty, inode, __func__))
 		return 0;
@@ -1714,8 +1715,11 @@ int tty_release(struct inode *inode, struct file *filp)
 		if (!do_sleep)
 			break;
 
-		printk(KERN_WARNING "%s: %s: read/write wait queue active!\n",
+		if (once) {
+			once = 0;
+			printk(KERN_WARNING "%s: %s: read/write wait queue active!\n",
 				__func__, tty_name(tty, buf));
+		}
 		tty_unlock();
 		mutex_unlock(&tty_mutex);
 		schedule_timeout_killable(timeout);