Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759345Ab0HEWWq (ORCPT ); Thu, 5 Aug 2010 18:22:46 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:59911 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756338Ab0HEWWn convert rfc822-to-8bit (ORCPT ); Thu, 5 Aug 2010 18:22:43 -0400 MIME-Version: 1.0 In-Reply-To: <20100805213851.GA13868@suse.de> References: <1280926108-24668-1-git-send-email-virtuoso@slind.org> <1280937526.28884.21.camel@work-vm> <1281042665.3405.15.camel@localhost.localdomain> <20100805213851.GA13868@suse.de> From: Kay Sievers Date: Fri, 6 Aug 2010 00:22:27 +0200 Message-ID: Subject: Re: [PATCH] [RFC] notify userspace about time changes To: Greg KH Cc: john stultz , Alexander Shishkin , lkml@vger.kernel.org, "Kirill A. Shutemov" , Thomas Gleixner , Martin Schwidefsky , Andrew Morton , Jon Hunter , Ingo Molnar , Peter Zijlstra , "Paul E. McKenney" , David Howells , Avi Kivity , "H. Peter Anvin" , John Kacur , linux-kernel@vger.kernel.org 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 Content-Length: 2129 Lines: 42 On Thu, Aug 5, 2010 at 23:38, Greg KH wrote: > On Thu, Aug 05, 2010 at 02:11:05PM -0700, john stultz wrote: >> On Thu, 2010-08-05 at 15:33 +0300, Alexander Shishkin wrote: >> > On 4 August 2010 18:58, john stultz wrote: >> > > Is there a actual use case that you need this for?  I don't really have >> > > an issue with the code I just really want to make sure the feature would >> > > be useful enough to justify the API and code maintenance going forward. >> > >> > Yes. What we have here is an application which takes care of different means >> > of time synchronization (trusted time servers, different GSM operators, etc) >> > and also different kinds of time-based events/notifications (like "dentist >> > appointment next thursday"). When it encounters a time change that is >> > made by some other application, it basically wants to disable automatic >> > time adjustment and trigger the events/notifications which are due at this >> > (new) time. >> >> Ok. Something specific is always more helpful then theoretical uses. >> >> I think the filtering is still a bit controversial, so you might want to >> respin it without that. But otherwise I'm ok with it as long as no one >> else objects to any of the minor details of the interface >> >> GregKH: Does /sys/kernel/time_notify seem ok by you? > > Um, it depends, what is that file going to do?  I don't see a > Documentation/ABI/ entry here that describes it fully :) I think that's really awkward interface, to pass file descriptor numbers around and write them to magic sysfs files. I would very much prefer a file that contains the current time, and wakes up possible users with a POLL_ERR on changes caused by some other process. That works very well for things like /proc/mounts, is easy to get, and does not need a full page of weird instructions to get stuff done. :) Kay -- 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/