Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932522Ab1EKQTU (ORCPT ); Wed, 11 May 2011 12:19:20 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:58844 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757474Ab1EKQTB (ORCPT ); Wed, 11 May 2011 12:19:01 -0400 Subject: Re: [tip:timers/core] timerfd: Allow timers to be cancelled when clock was set From: Peter Zijlstra To: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, kay.sievers@vrfy.org, johnstul@us.ibm.com, davidel@xmailserver.org, virtuoso@slind.org, tglx@linutronix.de, chris.friesen@genband.com, kirill@shutemov.name Cc: linux-tip-commits@vger.kernel.org In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Wed, 11 May 2011 12:23:53 +0200 Message-ID: <1305109433.2914.208.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1639 Lines: 36 On Mon, 2011-05-02 at 19:44 +0000, tip-bot for Thomas Gleixner wrote: > Commit-ID: 99ee5315dac6211e972fa3f23bcc9a0343ff58c4 > Gitweb: http://git.kernel.org/tip/99ee5315dac6211e972fa3f23bcc9a0343ff58c4 > Author: Thomas Gleixner > AuthorDate: Wed, 27 Apr 2011 14:16:42 +0200 > Committer: Thomas Gleixner > CommitDate: Mon, 2 May 2011 21:39:15 +0200 > > timerfd: Allow timers to be cancelled when clock was set > > Some applications must be aware of clock realtime being set > backward. A simple example is a clock applet which arms a timer for > the next minute display. If clock realtime is set backward then the > applet displays a stale time for the amount of time which the clock > was set backwards. Due to that applications poll the time because we > don't have an interface. Shouldn't that clock applet use CLOCK_MONOTONIC for the timer anyway? Furthermore, weren't there patches to provide clkadjust notifiers? In which case we can have the app woken up and it can fiddle its own timers. > Extend the timerfd interface by adding a flag which puts the timer > onto a different internal realtime clock. All timers on this clock are > expired whenever the clock was set. I don't much like adding random clocks like that, the extra timer base makes many timer operations more expensive, and I really don't see this being worth it :/ -- 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/