From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757465Ab3GEQFN (ORCPT ); Fri, 5 Jul 2013 12:05:13 -0400 Received: from www.linutronix.de ([62.245.132.108]:45830 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757360Ab3GEQFM (ORCPT ); Fri, 5 Jul 2013 12:05:12 -0400 Date: Fri, 5 Jul 2013 18:05:14 +0200 (CEST) From: Thomas Gleixner To: =?ISO-8859-15?Q?S=F6ren_Brinkmann?= cc: John Stultz , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Michal Simek Subject: Re: [PATCH] clocksource/cadence_ttc: Reuse clocksource as sched_clock In-Reply-To: Message-ID: References: <1372888216-10726-1-git-send-email-soren.brinkmann@xilinx.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323329-193646010-1373040314=:32106" X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-193646010-1373040314=:32106 Content-Type: TEXT/PLAIN; charset=utf-8 Content-Transfer-Encoding: 8BIT On Fri, 5 Jul 2013, Sören Brinkmann wrote: > On Fri, Jul 05, 2013 at 08:30:47AM +0200, Thomas Gleixner wrote: > > On Wed, 3 Jul 2013, Soren Brinkmann wrote: > > > > > Reuse the TTC clocksource timer as sched clock, too. Since only a single > > > sched clock is supported in Linux, this feature optional and can be > > > selected through Kconfig. > > > > This changelog doesn't make sense. > > > > There can be only one active sched_clock, but that does no mean, that > > you cannot have different implementations compiled in. > > > > So if you disable this config which sched_clock is your kernel using? > Jiffies > > > And if you enable it, how is guaranteed that you end up with the ttc > > sched_clock as the active one? Just due to initcall ordering? > I assumed so. Is there a different mechanism? jiffies is the default one. If you setup an explicit sched clock then this is used. initcall ordering only matters if you have two possible sched clocks which might replace jiffies. The one which gets registered last wins. So the question is, why you want to disable your sched clock at compile time. Thanks, tglx --8323329-193646010-1373040314=:32106--