From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761179AbZBEA0a (ORCPT ); Wed, 4 Feb 2009 19:26:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756181AbZBEAZ4 (ORCPT ); Wed, 4 Feb 2009 19:25:56 -0500 Received: from x35.xmailserver.org ([64.71.152.41]:57016 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753478AbZBEAZy (ORCPT ); Wed, 4 Feb 2009 19:25:54 -0500 X-AuthUser: davidel@xmailserver.org Date: Wed, 4 Feb 2009 16:25:52 -0800 (PST) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Andrew Morton cc: Michael Kerrisk , mtk.manpages@googlemail.com, Linux Kernel Mailing List , Linus Torvalds , linux-api@vger.kernel.org Subject: Re: [patch/rfc] eventfd semaphore-like behavior In-Reply-To: <20090204161816.b93a4588.akpm@linux-foundation.org> Message-ID: References: <20090204150507.665b5b7c.akpm@linux-foundation.org> <20090204152434.c8f65d52.akpm@linux-foundation.org> <20090204155514.6abbdc8f.akpm@linux-foundation.org> <20090204161816.b93a4588.akpm@linux-foundation.org> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 4 Feb 2009, Andrew Morton wrote: > On Thu, 5 Feb 2009 12:59:07 +1300 > Michael Kerrisk wrote: > > > >> > > > What should be userspace's fallback strategy if that support is not > > >> > > > present? > > >> > > > > >> > > #ifdef EFD_SEMAPHORE, maybe? > > >> > > > >> > That's compile-time. People who ship binaries will probably want > > >> > to find a runtime thing for back-compatibility. > > >> > > >> I dunno. How do they actually do when we add new flags, like the O_ ones? > > >> > > > > > > Dunno. Probably try the syscall and see if it returned -EINVAL. Does > > > that work in this case? > > > > As youll have seen by now, Ulrich and I noted that it works. > > I think you means "should work" ;) > > We're talking about this, yes? > > SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) > { > int fd; > struct eventfd_ctx *ctx; > > /* Check the EFD_* constants for consistency. */ > BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC); > BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK); > > if (flags & ~(EFD_CLOEXEC | EFD_NONBLOCK)) > return -EINVAL; > > That looks like it should work to me. I lost you guys. On old kernels you'd get -EINVAL when using the new flag. Wasn't it clear? Or is there some side-band traffic in this conversation that I missed? :) - Davide