From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753461Ab0IQLPJ (ORCPT ); Fri, 17 Sep 2010 07:15:09 -0400 Received: from filtteri1.pp.htv.fi ([213.243.153.184]:45876 "EHLO filtteri1.pp.htv.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751660Ab0IQLPI (ORCPT ); Fri, 17 Sep 2010 07:15:08 -0400 Date: Fri, 17 Sep 2010 14:08:03 +0300 From: Alexander Shishkin To: Kay Sievers Cc: Alan Cox , linux-kernel@vger.kernel.org, John Stultz , Andrew Morton , "H. Peter Anvin" , Greg KH , Chris Friesen , Linus Torvalds , "Kirill A. Shutemov" , Thomas Gleixner , Martin Schwidefsky , Jon Hunter , Ingo Molnar , Peter Zijlstra , "Paul E. McKenney" , David Howells , Avi Kivity , John Kacur , Alexander Shishkin Subject: Re: [PATCH 1/7] notify userspace about time changes Message-ID: <20100917110803.GC10463@shisha.kicks-ass.net> References: <1284675049-23479-1-git-send-email-virtuoso@slind.org> <1284675049-23479-2-git-send-email-virtuoso@slind.org> <20100917113325.147734b6@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 17, 2010 at 12:22:36 +0200, Kay Sievers wrote: > On Fri, Sep 17, 2010 at 12:33, Alan Cox wrote: > >> Certain userspace applications (like "clock" desktop applets or cron) might > >> want to be notified when some other application changes the system time. It > >> might also be important for an application to be able to distinguish between > >> its own and somebody else's time changes. > > > > A program that cannot work out if it or someone else changed the time is > > very very broken indeed ! > > Yeah, that seems a bit weird to me too. Ok, I get it. Filtering has to go. > > Clocks apps don't care because they check the actual time so notice it > > shfited. Cron and anacron appear to contain the needed internal handling. > > Cron wakes up every minute to check if the time has changed. We don't > want such silly behavior, but there are no other options at the moment > for scheduling re-occurring events. > > > Anything sleeping until a time occurs maybe ? In which case its a lot > > simpler and cleaner than events to provide a new itimer which wakes the > > process when the wall time hits the time specified in the timer. > > That seems not sufficient. The details should be in the changelog of the patch. Yes, I did include your description of the problem in the 0/7, but that doesn't seem sufficient. I really need to compile all the usecases from previous threads and include them in 1/7 as well. Regards, -- Alex