From owner-cvs-all@FreeBSD.ORG Sat Aug 9 10:28:00 2008 Return-Path: Delivered-To: cvs-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0911F106564A; Sat, 9 Aug 2008 10:28:00 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.freebsd.org (Postfix) with ESMTP id B3FEA8FC31; Sat, 9 Aug 2008 10:27:59 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id 3FD5446C70; Sat, 9 Aug 2008 06:27:58 -0400 (EDT) Date: Sat, 9 Aug 2008 11:27:58 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Peter Jeremy In-Reply-To: <20080809001256.GL64458@server.vk2pj.dyndns.org> Message-ID: References: <200808081343.m78DhwYE068477@repoman.freebsd.org> <200808081226.32089.jhb@freebsd.org> <20080809001256.GL64458@server.vk2pj.dyndns.org> User-Agent: Alpine 1.10 (BSF 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Ed Schouten , cvs-all@freebsd.org, John Baldwin Subject: Re: cvs commit: src/sys/dev/io iodev.c X-BeenThere: cvs-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the entire tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 09 Aug 2008 10:28:00 -0000 On Sat, 9 Aug 2008, Peter Jeremy wrote: > On 2008-Aug-08 12:26:31 -0400, John Baldwin wrote: >> It should be setting D_TRACKCLOSE though so that close() reliably clears >> the flag even in single-threaded processes. You can still get odd behavior >> if you explicitly open it twice in an app and then close one of the two >> fd's. You will no longer have IO permission even though you still have one >> fd open. However, if you do that I think you deserve what you asked for. :) > > That behaviour may be legitimate: Your code links with libraries foo and > bar that each independently open /dev/io so they can frob different things > in IO space. libfoo needs ongoing access to device foo and so keeps its > descriptor open. libbar only needs once-off access to device bar and so > closes /dev/io once it's finished its initialisation. Libraries foo and bar > are completely independent and shouldn't need to know anything about each > other and your app shouldn't need to know that libraries it's using frob > around in IO space. If that's the view, there should probably be a per-process counter, although this is all a bit tricky anyway since file descriptors and processes have a tenuous relationship. Robert N M Watson Computer Laboratory University of Cambridge