X-Recipient:	archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status:	No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,SPF_SOFTFAIL
X-Spam-Check-By:	sourceware.org
Message-ID:	<4A51F83B.4060109@byu.net>
Date:	Mon, 06 Jul 2009 07:12:27 -0600
From:	Eric Blake <ebb9 AT byu DOT net>
User-Agent:	Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.22) Gecko/20090605 Thunderbird/2.0.0.22 Mnenhy/0.7.6.666
MIME-Version:	1.0
To:	cygwin AT cygwin DOT com
Subject:	Re: [1.7] fifo regression
References:	<4A51F60F DOT 2030304 AT byu DOT net>
In-Reply-To:	<4A51F60F.2030304@byu.net>
X-IsSubscribed:	yes
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

According to Eric Blake on 7/6/2009 7:03 AM:
> But on cygwin 1.7, when you attempt to create multiple writers to a single
> fifo, the second writer creates an fd just fine but then fails on any
> attempt to write to that fd:
> 
> $ mkfifo fifo
> $ (exec 5>fifo; sleep 25; echo one >&5)&
> [1] 4200
> $ (exec 5>fifo; sleep 15; echo two >&5)&
> [2] 204

It appears that part of the problem is that cygwin is violating POSIX - a
process that opens a fifo for writes must block until a corresponding
process opens the same fifo for reads, but cygwin is creating the fd
without blocking.  A pstree at this point shows that the sleep processes
have already been spawned...

> $ exec 5<fifo

...even though on Linux, the sleeps cannot spawn until after this point.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             ebb9 AT byu DOT net
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iEYEARECAAYFAkpR+DsACgkQ84KuGfSFAYBfLQCfY+IozoBQWjQaohizEcOjgXLt
CMYAoMTHprULJoeVp+i38N4Kjrv/HCHq
=VCM7
-----END PGP SIGNATURE-----

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

- Raw text -