Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760075Ab0HEKFj (ORCPT ); Thu, 5 Aug 2010 06:05:39 -0400 Received: from shutemov.name ([188.40.19.243]:36236 "EHLO shutemov.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755601Ab0HEKFg (ORCPT ); Thu, 5 Aug 2010 06:05:36 -0400 Date: Thu, 5 Aug 2010 13:05:35 +0300 From: "Kirill A. Shutemov" To: lkml@vger.kernel.org, Thomas Gleixner , John Stultz , 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, linux-api@vger.kernel.org Subject: Re: [PATCH] [RFC] notify userspace about time changes Message-ID: <20100805100535.GA1754@shutemov.name> References: <1280926108-24668-1-git-send-email-virtuoso@slind.org> <20100804153221.GA29109@shutemov.name> <20100804154638.GB28519@shisha.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100804154638.GB28519@shisha.kicks-ass.net> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1798 Lines: 35 On Wed, Aug 04, 2010 at 06:46:38PM +0300, Alexander Shishkin wrote: > On Wed, Aug 04, 2010 at 06:32:21 +0300, Kirill A. Shutemov wrote: > > On Wed, Aug 04, 2010 at 03:48:28PM +0300, Alexander Shishkin wrote: > > > Certain userspace applications (like "clock" desktop applets or ntpd) 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. > > > > > > This patch implements a notification interface via eventfd mechanism. Proccess > > > wishing to be notified about time changes should create an eventfd and echo > > > its file descriptor to /sys/kernel/time_notify. After that, any calls to > > > settimeofday()/stime()/adjtimex() made by other processes will be signalled > > > to this eventfd. Credits for suggesting the eventfd mechanism for this > > > purpose go te Kirill Shutemov. > > > > > > So far, this implementation can only filter out notifications caused by > > > time change calls made by the process that wrote the eventfd descriptor to > > > sysfs, but not its children which (might) have inherited the eventfd. It > > > is so far not clear to me whether this is bad and more confusing than > > > excluding such children as well. > > > > I think it's a bad idea to filter notifications. Let's leave it for > > Why? Someone might want to recieve notifications about its own activity. It's a policy. Kernel should provide mechanism, not policy. -- Kirill A. Shutemov -- 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/