From owner-freebsd-hackers  Wed Sep 18 21: 9:28 2002
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 E92C337B401
	for <hackers@FreeBSD.org>; Wed, 18 Sep 2002 21:09:27 -0700 (PDT)
Received: from khavrinen.lcs.mit.edu (khavrinen.lcs.mit.edu [18.24.4.193])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 5E74B43E65
	for <hackers@FreeBSD.org>; Wed, 18 Sep 2002 21:09:27 -0700 (PDT)
	(envelope-from wollman@khavrinen.lcs.mit.edu)
Received: from khavrinen.lcs.mit.edu (localhost [IPv6:::1])
	by khavrinen.lcs.mit.edu (8.12.3/8.12.5) with ESMTP id g8J49QVo045800
	(version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=OK);
	Thu, 19 Sep 2002 00:09:26 -0400 (EDT)
	(envelope-from wollman@khavrinen.lcs.mit.edu)
Received: (from wollman@localhost)
	by khavrinen.lcs.mit.edu (8.12.3/8.12.5/Submit) id g8J49QcN045797;
	Thu, 19 Sep 2002 00:09:26 -0400 (EDT)
	(envelope-from wollman)
Date: Thu, 19 Sep 2002 00:09:26 -0400 (EDT)
From: Garrett Wollman <wollman@lcs.mit.edu>
Message-Id: <200209190409.g8J49QcN045797@khavrinen.lcs.mit.edu>
To: Daniel Eischen <eischen@pcnet1.pcnet.com>
Cc: hackers@FreeBSD.org
Subject: Re: sem_init help?
In-Reply-To: <Pine.GSO.4.10.10209182206210.3071-100000@pcnet1.pcnet.com>
References: <20020919015911.GQ86737@elvis.mu.org>
	<Pine.GSO.4.10.10209182206210.3071-100000@pcnet1.pcnet.com>
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-hackers.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-hackers>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-hackers>
X-Loop: FreeBSD.ORG

<<On Wed, 18 Sep 2002 22:16:07 -0400 (EDT), Daniel Eischen <eischen@pcnet1.pcnet.com> said:

> The semaphore remains active until it is destroyed.  If you don't
> want to track its page, can you hook it into ipcrm(1)?

A simple way of implementing process-shared anonymous semaphores,
using the kernel support, is to simply create a temporary semaphore,
and (important part) store the pathname in the sem_t.  Then, every
semaphore operation becomes sem_open, kernel operation, sem_close, and
destroy unlinks the temporary semaphore.

This would be a poor-quality implementation, but it would work.  A
better implementation would not use a temporary semaphore at all.

-GAWollman


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message