Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161729AbXEBGQI (ORCPT ); Wed, 2 May 2007 02:16:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161730AbXEBGQI (ORCPT ); Wed, 2 May 2007 02:16:08 -0400 Received: from haxent.com ([65.99.219.155]:3902 "EHLO haxent.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161746AbXEBGQG convert rfc822-to-8bit (ORCPT ); Wed, 2 May 2007 02:16:06 -0400 Message-ID: <46382CA2.1020504@haxent.com.br> Date: Wed, 02 May 2007 03:16:02 -0300 From: Davi Arnaut MIME-Version: 1.0 To: Eric Dumazet Cc: Andrew Morton , Davide Libenzi , Linus Torvalds , Linux Kernel Mailing List Subject: Re: [patch 14/22] pollfs: pollable futex References: <20070502052235.914764000@haxent.com.br> <20070502053427.123392000@haxent.com.br> <4638279A.9010105@cosmosbay.com> In-Reply-To: <4638279A.9010105@cosmosbay.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2682 Lines: 91 Eric Dumazet wrote: > Davi Arnaut a ?crit : >> Asynchronously wait for FUTEX_WAKE operation on a futex if it still contains >> a given value. There can be only one futex wait per file descriptor. However, >> it can be rearmed (possibly at a different address) anytime. >> >> The pollable futex approach is far superior (send and receive events from >> userspace or kernel) to eventfd and fixes (supercedes) FUTEX_FD at the same time. >> >> Building block for pollable semaphores and user-defined events. >> >> Signed-off-by: Davi E. M. Arnaut >> >> --- >> fs/pollfs/Makefile | 1 >> fs/pollfs/futex.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++++ >> init/Kconfig | 7 ++ >> 3 files changed, 162 insertions(+) >> >> Index: linux-2.6/fs/pollfs/Makefile >> =================================================================== >> --- linux-2.6.orig/fs/pollfs/Makefile >> +++ linux-2.6/fs/pollfs/Makefile >> @@ -3,3 +3,4 @@ pollfs-y := file.o >> >> pollfs-$(CONFIG_POLLFS_SIGNAL) += signal.o >> pollfs-$(CONFIG_POLLFS_TIMER) += timer.o >> +pollfs-$(CONFIG_POLLFS_FUTEX) += futex.o >> Index: linux-2.6/fs/pollfs/futex.c >> =================================================================== >> --- /dev/null >> +++ linux-2.6/fs/pollfs/futex.c >> @@ -0,0 +1,154 @@ >> +/* >> + * pollable futex >> + * >> + * Copyright (C) 2007 Davi E. M. Arnaut >> + * >> + * Licensed under the GNU GPL. See the file COPYING for details. >> + */ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +struct futex_event { >> + union { >> + void __user *addr; >> + u64 padding; >> + }; >> + int val; >> +}; > > Hum... Here we might have a problem with 64 bit futexes, or private futexes > > So I believe this interface is not well defined and not expandable: in case of > future additions to futexes, an old application compiled with an old pollable > futex_event type might fail. > Hmm, how about: struct futex_event { union { void __user *addr; u64 padding; }; union { int val; s64 val64; }; /* whatever room is necessary for future improvements */ }; I haven't been keeping up with 64 bit or private futexes. What else could probably go wrong? -- Davi Arnaut - 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/