From owner-freebsd-hackers@FreeBSD.ORG  Thu Jan 13 12:45:01 2005
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 699A716A4CE
	for <freebsd-hackers@freebsd.org>;
	Thu, 13 Jan 2005 12:45:01 +0000 (GMT)
Received: from smtp1.adl2.internode.on.net (smtp1.adl2.internode.on.net
	[203.16.214.181])
	by mx1.FreeBSD.org (Postfix) with ESMTP id B324343D39
	for <freebsd-hackers@freebsd.org>;
	Thu, 13 Jan 2005 12:45:00 +0000 (GMT)
	(envelope-from smckay@internode.on.net)
Received: from dungeon.home (ppp231-141.lns1.bne1.internode.on.net
	[203.122.231.141])j0DCiwsW089760;
	Thu, 13 Jan 2005 23:14:59 +1030 (CST)
Received: from dungeon.home (localhost [127.0.0.1])
	by dungeon.home (8.13.1/8.11.6) with ESMTP id j0DCiGga008717;
	Thu, 13 Jan 2005 22:44:16 +1000 (EST)
	(envelope-from mckay)
Message-Id: <200501131244.j0DCiGga008717@dungeon.home>
To: Jilles Tjoelker <jilles@stack.nl>
References: <200501120949.j0C9nQCZ000573@dungeon.home>
	<200501121354.j0CDscrR002027@dungeon.home>
	<20050113074721.GC79646@cirb503493.alcatel.com.au>
	<20050113110558.GA27286@stack.nl>
In-Reply-To: <20050113110558.GA27286@stack.nl>
    from Jilles Tjoelker at "Thu, 13 Jan 2005 12:05:58 +0100"
Date: Thu, 13 Jan 2005 22:44:16 +1000
From: Stephen McKay <smckay@internode.on.net>
cc: Peter Jeremy <PeterJeremy@optushome.com.au>
cc: freebsd-hackers@freebsd.org
cc: Stephen McKay <smckay@internode.on.net>
Subject: Re: Background processes setting O_NONBLOCK on ttys 
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 13 Jan 2005 12:45:01 -0000

On Thursday, 13th January 2005, Jilles Tjoelker wrote:

>POSIX states that the O_NONBLOCK flag is per open file description. File
>descriptors created with dup(2), fork(2) or similar methods share the
>same open file description, while new descriptors created with open(2)
>do not.

Can you quote chapter and verse on this?  Or is it merely implied?  A pointer
to an online copy would be best.

I found that "The Open Group Base Specifications Issue 6" at
http://www.opengroup.org/onlinepubs/009695399/toc.htm is not clear
on the matter.  Also "The Single UNIX Specification, Version 2" at
http://www.opengroup.org/onlinepubs/007908799/ is similarly unclear.

>Consequently, a POSIX-compliant implementation of O_NONBLOCK does not
>solve the problem, as all descriptors to the terminal refer to the same
>open file description. O_NONBLOCK is indeed unusable for descriptions
>shared with other unknowing processes :(

If we must be POSIX compliant and if you accept that POSIX demands that
dup'd file descriptors share a single O_NONBLOCK flag, then the logical
end position is that the threads library must not routinely set stdin,
stdout and stderr to non-blocking.  Right?

Personally, I have no qualms being non-POSIX compliant in a good cause.
Wouldn't being non-POSIX on this issue be easier?

Hmm.  Should this be on -arch now?

Stephen.