Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754108AbXE3PlI (ORCPT ); Wed, 30 May 2007 11:41:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752947AbXE3Pkz (ORCPT ); Wed, 30 May 2007 11:40:55 -0400 Received: from mx1.redhat.com ([66.187.233.31]:37131 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751971AbXE3Pkx (ORCPT ); Wed, 30 May 2007 11:40:53 -0400 Message-ID: <465D9A97.40507@redhat.com> Date: Wed, 30 May 2007 08:39:03 -0700 From: Ulrich Drepper Organization: Red Hat, Inc. User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Ingo Molnar CC: Jeff Garzik , Zach Brown , linux-kernel@vger.kernel.org, Linus Torvalds , Arjan van de Ven , Christoph Hellwig , Andrew Morton , Alan Cox , Evgeniy Polyakov , "David S. Miller" , Suparna Bhattacharya , Davide Libenzi , Jens Axboe , Thomas Gleixner Subject: Re: Syslets, Threadlets, generic AIO support, v6 References: <20070529212718.GH7875@mami.zabbo.net> <465CA654.5000505@garzik.org> <20070530072055.GA3077@elte.hu> <465D286E.2080807@redhat.com> <20070530084252.GA15708@elte.hu> In-Reply-To: <20070530084252.GA15708@elte.hu> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2289 Lines: 56 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Ingo Molnar wrote: > we should perhaps enable glibc to have its separate fd namespace (or > 'hidden' file descriptors at the upper end of the fd space) so that it > can transparently listen to netlink events (or do epoll), Something like this would only work reliably if you have actual protection coming with it. Also, there are still reasons why an application might want to see, close, handle, whatever these descriptors in a separate namespace. I think such namespaces are a broken concept. How many do you want to introduce? Plus, then you get away from the normal file descriptor interfaces anyway. If you'd represent these alternative namespace descriptors with ordinary ints you gain nothing. You'd have to use tuples (namespace,descriptor) and then you need a whole set of new interfaces or some sticky namespace selection which will only cause problems (think signal delivery). > without > impacting the application fd namespace - instead of ducking to a memory > based API as a workaround. It's not "ducking". Memory mapping is one of the most natural interfaces. Just because Unix/Linux is built around the concept of file descriptors does not mean this is the ultimate in usability. File descriptors are in fact clumsy: if you have a file descriptor to read and write data, all auxiliary data for that communication must be transferred out-of-band (e.g, fcntl) or in very magical and hard to use ways (recvmsg, sendmsg). With a memory based event mechanism this auxiliary data can be stored in memory along with the event notification. > it is a serious flexibility issue that should not be ignored. The > unified fd space is a blessing on one hand because it's simple and Too simple. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQFGXZqX2ijCOnn/RHQRAsSFAKCNrd8/sRss1wBA9hkpnYIeALDbXQCfRNAb yZy2Nofz2CgDo9PQYK3C/bo= =klUJ -----END PGP SIGNATURE----- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/