From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1757943Ab2IMMrs (ORCPT <rfc822;w@1wt.eu>);
	Thu, 13 Sep 2012 08:47:48 -0400
Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:56931 "EHLO
	lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753203Ab2IMMrr (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 13 Sep 2012 08:47:47 -0400
Date: Thu, 13 Sep 2012 13:51:31 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: LKML <linux-kernel@vger.kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Pavel Emelyanov <xemul@parallels.com>
Subject: Re: [RFC] tty: Add get- ioctls to fetch tty status
Message-ID: <20120913135131.5b251797@pyramind.ukuu.org.uk>
In-Reply-To: <20120913095623.GB28508@moon>
References: <20120913095623.GB28508@moon>
X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.8; x86_64-redhat-linux-gnu)
Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAFVBMVEWysKsSBQMIAwIZCwj///8wIhxoRDXH9QHCAAABeUlEQVQ4jaXTvW7DIBAAYCQTzz2hdq+rdg494ZmBeE5KYHZjm/d/hJ6NfzBJpp5kRb5PHJwvMPMk2L9As5Y9AmYRBL+HAyJKeOU5aHRhsAAvORQ+UEgAvgddj/lwAXndw2laEDqA4x6KEBhjYRCg9tBFCOuJFxg2OKegbWjbsRTk8PPhKPD7HcRxB7cqhgBRp9Dcqs+B8v4CQvFdqeot3Kov6hBUn0AJitrzY+sgUuiA8i0r7+B3AfqKcN6t8M6HtqQ+AOoELCikgQSbgabKaJW3kn5lBs47JSGDhhLKDUh1UMipwwinMYPTBuIBjEclSaGZUk9hDlTb5sUTYN2SFFQuPe4Gox1X0FZOufjgBiV1Vls7b+GvK3SU4wfmcGo9rPPQzgIabfj4TYQo15k3bTHX9RIw/kniir5YbtJF4jkFG+dsDK1IgE413zAthU/vR2HVMmFUPIHTvF6jWCpFaGw/A3qWgnbxpSm9MSmY5b3pM1gvNc/gQfwBsGwF0VCtxZgAAAAASUVORK5CYII=
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> +static int pty_get_lock(struct tty_struct *tty, int __user *arg)
> +{
> +	int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
> +	if (put_user(locked, arg))
> +		return -EFAULT;

Now explain exactly how this doesn't race with another thread chanigng
the lock setting ?

The other comment I have is that it might be better put these in now
there are sysfs patches for the tty layer bouncing about to provide the
needed infrastructure ?

Alan