From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753567AbYEaDPA (ORCPT ); Fri, 30 May 2008 23:15:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750801AbYEaDOt (ORCPT ); Fri, 30 May 2008 23:14:49 -0400 Received: from mx1.redhat.com ([66.187.233.31]:53048 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750705AbYEaDOs (ORCPT ); Fri, 30 May 2008 23:14:48 -0400 Message-ID: <4840C29B.6030507@redhat.com> Date: Fri, 30 May 2008 20:14:35 -0700 From: Ulrich Drepper Organization: Red Hat, Inc. User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Linus Torvalds CC: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mtk.manpages@gmail.com Subject: Re: [PATCH 0/3] 64-bit futexes: Intro References: <200805310127.m4V1RLR4013808@devserv.devel.redhat.com> In-Reply-To: X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Linus Torvalds wrote: > We've had a 32-bit rwsemaphore in the kernel for a *long* time. You misread what I wrote. Semaphores are fine. The problem are reader/writer locks where we need three counters and some flags. It is absolutely not acceptable to limit the number of threads to 512 to make this fit. > I think it's totally stupid for glibc to even *try* to do something like > this, since almost nobody will have a kernel with 64-bit futex support for > a long time in the wild anyway. So you need to support a 32-bit semaphore > in practice, and it's been done before. Again, misread. This is not functionality which is not available. Semaphores are *of course* fine with 32 bits. And there is a reader/writer lock implementation. It is just very slow compared to what is possible. The transition between systems miss the 64-bit support and those which have it is completely transparent. The same glibc binary will work for both. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkhAwpsACgkQ2ijCOnn/RHS7PACdGvdgI9pv+IcsSPkXPVwFJ5ZF YNQAn01fm1wEc4EI/fwOVuM57XtCy9Dq =LcpJ -----END PGP SIGNATURE-----