From owner-freebsd-current@FreeBSD.ORG Wed Dec 22 00:05:05 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 1F98516A4CE; Wed, 22 Dec 2004 00:05:05 +0000 (GMT) Received: from fledge.watson.org (fledge.watson.org [204.156.12.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id AF66843D1D; Wed, 22 Dec 2004 00:05:04 +0000 (GMT) (envelope-from robert@fledge.watson.org) Received: from fledge.watson.org (localhost [127.0.0.1]) by fledge.watson.org (8.13.1/8.13.1) with ESMTP id iBM022Hg063387; Tue, 21 Dec 2004 19:02:02 -0500 (EST) (envelope-from robert@fledge.watson.org) Received: from localhost (robert@localhost)iBM01p6F063382; Wed, 22 Dec 2004 00:02:02 GMT (envelope-from robert@fledge.watson.org) Date: Wed, 22 Dec 2004 00:01:51 +0000 (GMT) From: Robert Watson X-Sender: robert@fledge.watson.org To: Joe Kelsey In-Reply-To: <1102975803.30309.196.camel@zircon.zircon.seattle.wa.us> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: arch@freebsd.org cc: stable@freebsd.org cc: hackers@freebsd.org cc: current@freebsd.org Subject: Re: Fixing Posix semaphores X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 22 Dec 2004 00:05:05 -0000 On Mon, 13 Dec 2004, Joe Kelsey wrote: > I have a desire to fix posix semaphores in at least 5.3. The current > implementation doesn't actually follow the "spirit" of the standard, > even though it technically qualifies in a somewhat degraded sense. I > refer to the fact that the current implementation treats posix > semaphores as completely contained inside the kernel and essentially > divorced from the filesystem. The true "spirit" of the standard places > the semaphores directly in the file system, similar to named pipes. > However the current implementation treats the supplied "name" as a > 14-character identifier, required to begin with a slash and contain no > other slashes. Pretty weak. > > Well, in order to fix this, we need to add file system code and come up > with a new type. I currently have some time to spend on something like > this and am willing to put in whatever effort it takes. Does anyone > want to add their own ideas or requirements? >From my perspective, the biggest win here is that it would permit different name spaces to trivially exist using multiple mountpoints of a "semfs". This would make it easy to allow applications in different jails to use identical names without colliding. FWIW, my only experience with POSIX semaphores on a system other than FreeBSD is on Darwin, where a similar model is used to that on FreeBSD: a flat kernel-maintained name space is present. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Principal Research Scientist, McAfee Research