Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935422Ab0HFHnt (ORCPT ); Fri, 6 Aug 2010 03:43:49 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:60731 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933570Ab0HFHnq convert rfc822-to-8bit (ORCPT ); Fri, 6 Aug 2010 03:43:46 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=ujM/+yvihIreqT3KQE2ph3ZQdDMXsAESXfVO6uYZi8E8VErnXMzqv1zaOEXK4KGJTM uJl6k+gSjh+tX9JsSv+vEcKr90jKFKmqj0fF5/JARuEjMGqI9R9nfZkUjEgZXCwpT5XB LZFs1z/6ly2+YOHeQMEseSfA1vqXkdnZojh1k= MIME-Version: 1.0 In-Reply-To: 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> Date: Fri, 6 Aug 2010 09:43:44 +0200 Message-ID: Subject: Re: [PATCH] [RFC] notify userspace about time changes From: Bastien ROUCARIES To: Kay Sievers Cc: Greg KH , 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=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2315 Lines: 45 On Fri, Aug 6, 2010 at 12:22 AM, Kay Sievers wrote: > 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. :) > See http://lwn.net/Articles/323658/ and it is plan9 compatible Bastien -- 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/