From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E770BC3279B for ; Tue, 10 Jul 2018 13:26:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB103208E3 for ; Tue, 10 Jul 2018 13:26:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AB103208E3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933336AbeGJNZ5 (ORCPT ); Tue, 10 Jul 2018 09:25:57 -0400 Received: from foss.arm.com ([217.140.101.70]:46410 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933138AbeGJNZ4 (ORCPT ); Tue, 10 Jul 2018 09:25:56 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0DDC8ED1; Tue, 10 Jul 2018 06:25:56 -0700 (PDT) Received: from [10.1.210.28] (unknown [10.1.210.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E81133F5A0; Tue, 10 Jul 2018 06:25:53 -0700 (PDT) Cc: Sudeep Holla , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Marc Zyngier , Kevin Hilman , Martin Blumenstingl , Mark Rutland Subject: Re: [PATCH 2/2] clocksource: arm_arch_timer: set arch_mem_timer cpumask to cpu_possible_mask To: Thomas Gleixner References: <1531151136-18297-1-git-send-email-sudeep.holla@arm.com> <1531151136-18297-2-git-send-email-sudeep.holla@arm.com> From: Sudeep Holla Organization: ARM Message-ID: Date: Tue, 10 Jul 2018 14:25:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/07/18 13:21, Thomas Gleixner wrote: > On Tue, 10 Jul 2018, Sudeep Holla wrote: > >> >> >> On 09/07/18 23:09, Thomas Gleixner wrote: >>> On Mon, 9 Jul 2018, Sudeep Holla wrote: >>> >>>> Currently, arch_mem_timer cpumask is set to cpu_all_mask which should be >>>> fine. However, cpu_possible_mask is more accurate and if there are other >>>> clockevent source in the system which are set to cpu_possible_mask, then >>>> having cpu_all_mask may result in issue. >>>> >>>> E.g. on a platform with arm,sp804 timer with rating 300 and >>>> cpu_possible_mask and this arch_mem_timer timer with rating 400 and >>>> cpu_all_mask, tick_check_preferred may choose both preferred as the >>>> cpumasks are not equal though they must be. >>>> >>>> This issue was root caused incorrectly initially and a fix was merged as >>>> commit 1332a9055801 ("tick: Prefer a lower rating device only if it's CPU >>>> local device"). >>> >>> To avoid that in the future we really should fix the decision logic to mask >>> out the non possible CPUs from the supplied masks. >> >> Sure, I can do that. But do you want that as a fix for v4.18 ? > > No, that's for 4.19 > Ah OK, I assume you are fine with this patch as fix for v4.18. >> I think we may need this check at another place in tick_setup_device >> >> 213 /* >> 214 * When the device is not per cpu, pin the interrupt to the >> 215 * current cpu: >> 216 */ >> 217 if (!cpumask_equal(newdev->cpumask, cpumask)) >> 218 irq_set_affinity(newdev->irq, cpumask); >> >> Does it make sense trim dev->cpumask when registering the clockevents >> device itself instead of adding check at place where this cpumask >> can be used ? So that any future user of those masks need not have to >> take care of that. > > The problem is you cannot trim it because cpu_all_mask is global and const. > Indeed, again forgot it just a pointer to the global one, duh! >> Also only few ARM clocksource drivers use cpu_all_mask which could be >> result of copy-paste, we can even fix them too. >> >> arm_arch_timer.c: clk->cpumask = cpu_all_mask; >> tegra20_timer.c: tegra_clockevent.cpumask = cpu_all_mask; >> timer-atcpit100.c: .cpumask = cpu_all_mask, >> timer-keystone.c: event_dev->cpumask = cpu_all_mask; >> zevio-timer.c: timer->clkevt.cpumask = cpu_all_mask; > > Yes, that makes sense. What we could do is warn, when cpu_all_mask is set > at registration time and replace the pointer with cpu_possible_mask. > I like this approach than having to bitwise and with cpu_possible_mask at all the necessary place. I will cook up a patch. -- Regards, Sudeep