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 503F4C3279B for ; Tue, 10 Jul 2018 12:21:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0755B20883 for ; Tue, 10 Jul 2018 12:21:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0755B20883 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de 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 S933216AbeGJMVo (ORCPT ); Tue, 10 Jul 2018 08:21:44 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:36464 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753275AbeGJMVn (ORCPT ); Tue, 10 Jul 2018 08:21:43 -0400 Received: from hsi-kbw-5-158-153-52.hsi19.kabel-badenwuerttemberg.de ([5.158.153.52] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1fcreH-00017r-55; Tue, 10 Jul 2018 14:21:41 +0200 Date: Tue, 10 Jul 2018 14:21:40 +0200 (CEST) From: Thomas Gleixner To: Sudeep Holla cc: 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 In-Reply-To: Message-ID: References: <1531151136-18297-1-git-send-email-sudeep.holla@arm.com> <1531151136-18297-2-git-send-email-sudeep.holla@arm.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > 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. > 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. Thanks, tglx