Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751659Ab0KXIGJ (ORCPT ); Wed, 24 Nov 2010 03:06:09 -0500 Received: from mail-bw0-f46.google.com ([209.85.214.46]:64338 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751393Ab0KXIGI (ORCPT ); Wed, 24 Nov 2010 03:06:08 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:reply-to:to:cc:in-reply-to:references:content-type :date:message-id:mime-version:x-mailer:content-transfer-encoding; b=nyWwQY/iLodXiFFwaejyyCHs6F2ARPajC2Gao6f0ItnWmOpdcTEepbzRSHsMCGJnPm 0HxaiGHUcnwHgZAuzMCOk0shDFKKJkU2CKTA51wXoQYeE1p9XJDtJxp4L6/WIYAt18p3 QvVJFWFgstjyvyHExKT9uWBhVg5NGhwn2dqIU= Subject: Re: [PATCH] [RFC] timerfd: add TFD_NOTIFY_CLOCK_SET to watch for clock changes From: Artem Bityutskiy Reply-To: dedekind1@gmail.com To: Lennart Poettering Cc: Alexander Shishkin , linux-kernel@vger.kernel.org, Thomas Gleixner , Alexander Viro , Greg Kroah-Hartman , Feng Tang , Andrew Morton , Michael Tokarev , Marcelo Tosatti , John Stultz , Chris Friesen , Kay Sievers , "Kirill A. Shutemov" , Davide Libenzi , linux-fsdevel@vger.kernel.org In-Reply-To: <20101123224346.GA19350@tango.0pointer.de> References: <1290532938-7332-1-git-send-email-virtuoso@slind.org> <20101123224346.GA19350@tango.0pointer.de> Content-Type: text/plain; charset="UTF-8" Date: Wed, 24 Nov 2010 10:05:35 +0200 Message-ID: <1290585935.2438.14.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 (2.32.1-1.fc14) Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1892 Lines: 42 On Tue, 2010-11-23 at 23:43 +0100, Lennart Poettering wrote: > On Tue, 23.11.10 19:22, Alexander Shishkin (virtuoso@slind.org) wrote: > > > Certain userspace applications (like "clock" desktop applets or cron or > > systemd) might want to be notified when some other application changes > > the system time. There are several known to me reasons for this: > > - avoiding periodic wakeups to poll time changes; > > - rearming CLOCK_REALTIME timers when said changes happen; > > - changing system timekeeping policy for system-wide time management > > programs; > > - keeping guest applications/operating systems running in emulators > > up to date. > > > > This is another attempt to approach notifying userspace about system > > clock changes. The other one is using an eventfd and a syscall [1]. In > > the course of discussing the necessity of a syscall for this kind of > > notifications, it was suggested that this functionality can be achieved > > via timers [2] (and timerfd in particular [3]). This idea got quite > > some support [4], [5], [6] and some vague criticism [7], so I decided > > to try and go a bit further with it. > > I agree with Kay, this is pretty much exactly what we want for > systemd. (Assuming that the time jump due to system suspend is > propagated to userspace like any other time jump with this path). A "Tested-by: Lennart Poettering " would be helpful, I think. > So yeah, I'd be very happy if this could be merged. Hmm, and question about why exactly the timerfd interface is a bad way to go was ignored. -- Best Regards, Artem Bityutskiy (Артём Битюцкий) -- 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/