Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757473AbXIET5l (ORCPT ); Wed, 5 Sep 2007 15:57:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755403AbXIET5d (ORCPT ); Wed, 5 Sep 2007 15:57:33 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:50061 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755122AbXIET5c (ORCPT ); Wed, 5 Sep 2007 15:57:32 -0400 X-AuthUser: davidel@xmailserver.org Date: Wed, 5 Sep 2007 12:57:24 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Michael Kerrisk cc: Andrew Morton , corbet@lwn.net, jengelh@computergmbh.de, hch@lst.de, stable@kernel.org, Ulrich Drepper , Linus Torvalds , Linux Kernel Mailing List , tglx@linutronix.de, rdunlap@xenotime.net Subject: Re: [PATCH] Revised timerfd() interface In-Reply-To: <20070905162352.236680@gmx.net> Message-ID: References: <20070825064114.107820@gmx.net> <46DD116C.4040301@gmx.net> <20070904011800.762523a4.akpm@linux-foundation.org> <20070904204932.208520@gmx.net> <20070905000831.313400@gmx.net> <20070905162352.236680@gmx.net> 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 X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1991 Lines: 46 On Wed, 5 Sep 2007, Michael Kerrisk wrote: > Hi Davide, > > > > > > As I think about this more, I see more problems with > > > > > your argument. timerfd needs the ability to get and > > > > > get-while-setting just as much as the earlier APIs. > > > > > Consider a library that creates a timerfd file descriptor that > > > > > is handed off to an application: that library may want > > > > > to modify the timer settings without having to create a > > > > > new file descriptor (the app mey not be able to be told about > > > > > the new fd). Your argument just doesn't hold, AFAICS. > > > > > > > > Such hypotethical library, in case it really wanted to offer such > > > > functionality, could simply return an handle instead of the raw fd, > > > > and take care of all that stuff in userspace. > > > > > > Did I miss something? Is it not the case that as soon as the > > > library returns a handle, rather than an fd, then the whole > > > advantage of timerfd() (being able to select/poll/epoll on > > > the timer as well as other fds) is lost? > > > > Why? The handle would simply be a little struct where the timerfd fd is > > stored, and a XXX_getfd() would return it. > > So my point is, I doubt such functionalities are really needed, and I > > also argue that the kernel is the best place for such wrapper code > > to go. > > So what happens if one thread (via the library) wants modify > a timer's settings at the same timer as another thread is > select()ing on it? The first thread can't do this by creating > a new timerfd timer, since it wants to affect the select() > in the other thread? It can be done w/out any problems. The select thread will be notified whenever the new timer setting expires. - Davide - 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/