Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754999Ab3JBRWj (ORCPT ); Wed, 2 Oct 2013 13:22:39 -0400 Received: from smtp.codeaurora.org ([198.145.11.231]:60920 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754984Ab3JBRWh (ORCPT ); Wed, 2 Oct 2013 13:22:37 -0400 Message-ID: <524C565C.8010709@codeaurora.org> Date: Wed, 02 Oct 2013 10:22:36 -0700 From: Stephen Boyd User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Santosh Shilimkar CC: Will Deacon , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "arm@kernel.org" , John Stultz , Russell King , "rob.herring@calxeda.com" , Thomas Gleixner , Daniel Lezcano Subject: Re: [PATCH] sched_clock: fix postinit no sched_clock function check References: <1380732928-13897-1-git-send-email-santosh.shilimkar@ti.com> <20131002170917.GB30298@mudshark.cambridge.arm.com> <524C5484.5000601@ti.com> In-Reply-To: <524C5484.5000601@ti.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1917 Lines: 37 On 10/02/13 10:14, Santosh Shilimkar wrote: > On Wednesday 02 October 2013 01:09 PM, Will Deacon wrote: >> On Wed, Oct 02, 2013 at 05:55:28PM +0100, Santosh Shilimkar wrote: >>> The sched_clock code uses 2 levels of function pointers, sched_clock_func() >>> and read_sched_clock() but the no sched_clock check in postinit() just >>> checks read_sched_clock(). >>> >>> This leads to kernel falling back to jiffy based sched clock even in >>> presence of sched_clock_func() which is not desirable. >>> >>> Fix the postinit() check to avoid the issue. Probably the issue is hidden >>> so far on most of the arm SOCs because of already existing sched_clock >>> registrations apart from arch_timer sched_clock. One can reproduce the >>> issue by just have arch_timer as sched_clock >> Isn't this just an issue with the arch timer driver not calling >> setup_sched_clock? Instead, we munge around with sched_clock_func directly, >> which doesn't appear to be the way anybody else deals with this. >> > I thought about that option as well but was not sure since even in that case > the check is not complete. We just ensure that function is popullated. Yes, nothing is actually broken because sched_clock_func() won't try to use the jiffy based read_sched_clock() function. I'm not sure we actually need this patch besides to remove a useless timer that updates the jiffy epoch. Can we wait until my 64-bit sched_clock patch series lands in 3.13? It looks like I still need an ack from Will or Catalin on the architected timer patch before the clocksource folks pick it up. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- 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/