From patchwork Wed Jul 22 03:00:05 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 6839151 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id DCE1BC05AC for ; Wed, 22 Jul 2015 02:33:23 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id CF7FF20544 for ; Wed, 22 Jul 2015 02:33:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF09320553 for ; Wed, 22 Jul 2015 02:33:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754066AbbGVCdU (ORCPT ); Tue, 21 Jul 2015 22:33:20 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:57713 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753422AbbGVCdT (ORCPT ); Tue, 21 Jul 2015 22:33:19 -0400 Received: from aerr155.neoplus.adsl.tpnet.pl (79.191.199.155) (HELO vostro.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer v0.80) id 711a286de9349c58; Wed, 22 Jul 2015 04:33:18 +0200 From: "Rafael J. Wysocki" To: Viresh Kumar Cc: "Rafael J. Wysocki" , Russell King - ARM Linux , Lists linaro-kernel , "linux-pm@vger.kernel.org" , open list Subject: Re: [PATCH] cpufreq: Avoid double addition/removal of sysfs links Date: Wed, 22 Jul 2015 05:00:05 +0200 Message-ID: <10898142.yiJePgsQ3c@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.1.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <6175136.CkGk6PGZKa@vostro.rjw.lan> References: <20150718163149.GP7557@n2100.arm.linux.org.uk> <6175136.CkGk6PGZKa@vostro.rjw.lan> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Wednesday, July 22, 2015 03:56:21 AM Rafael J. Wysocki wrote: > On Wednesday, July 22, 2015 01:15:01 AM Rafael J. Wysocki wrote: > > Hi VIresh, > > > > On Mon, Jul 20, 2015 at 11:47 AM, Viresh Kumar wrote: > > > Consider a dual core (0/1) system with two CPUs: > > > - sharing clock/voltage rails and hence cpufreq-policy > > > - CPU1 is offline while the cpufreq driver is registered > > > > > > - cpufreq_add_dev() is called from subsys callback for CPU0 and we > > > create the policy for the CPUs and create link for CPU1. > > > - cpufreq_add_dev() is called from subsys callback for CPU1, we find > > > that the cpu is offline and we try to create a sysfs link for CPU1. > > > > So the problem is that the cpu_is_offline(cpu) check in > > cpufreq_add_dev() matches two distinct cases: (1) the CPU was not > > present before and it is just being hot-added and (2) the CPU is > > initially offline, but present, and this is the first time its device > > is registered. In the first case we can expect that the CPU will > > become online shortly (although that is not guaranteed too), but in > > the second case that very well may not happen. > > > > We need to be able to distinguish between those two cases and your > > patch does that, but I'm not sure if this really is the most > > straightforward way to do it. > > It looks like we need a mask of related CPUs that are present. Or, > alternatively, a mask of CPUs that would have been related had they > been present. > > That's sort of what your patch is adding, but not quite. OK, below is my take on this (untested), on top of https://patchwork.kernel.org/patch/6839031/ We still only create policies for online CPUs which may be confusing in some cases, but that's because drivers may not be able to handle CPUs that aren't online. --- drivers/cpufreq/cpufreq.c | 41 +++++++++++++++++++++++++---------------- include/linux/cpufreq.h | 1 + 2 files changed, 26 insertions(+), 16 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Index: linux-pm/include/linux/cpufreq.h =================================================================== --- linux-pm.orig/include/linux/cpufreq.h +++ linux-pm/include/linux/cpufreq.h @@ -62,6 +62,7 @@ struct cpufreq_policy { /* CPUs sharing clock, require sw coordination */ cpumask_var_t cpus; /* Online CPUs only */ cpumask_var_t related_cpus; /* Online + Offline CPUs */ + cpumask_var_t real_cpus; /* Related and present */ unsigned int shared_type; /* ACPI: ANY or ALL affected CPUs should set cpufreq */ Index: linux-pm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq.c +++ linux-pm/drivers/cpufreq/cpufreq.c @@ -1002,7 +1002,7 @@ static int cpufreq_add_dev_symlink(struc int ret = 0; /* Some related CPUs might not be present (physically hotplugged) */ - for_each_cpu_and(j, policy->related_cpus, cpu_present_mask) { + for_each_cpu(j, policy->real_cpus) { if (j == policy->kobj_cpu) continue; @@ -1019,7 +1019,7 @@ static void cpufreq_remove_dev_symlink(s unsigned int j; /* Some related CPUs might not be present (physically hotplugged) */ - for_each_cpu_and(j, policy->related_cpus, cpu_present_mask) { + for_each_cpu(j, policy->real_cpus) { if (j == policy->kobj_cpu) continue; @@ -1157,11 +1157,14 @@ static struct cpufreq_policy *cpufreq_po if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL)) goto err_free_cpumask; + if (!zalloc_cpumask_var(&policy->real_cpus, GFP_KERNEL)) + goto err_free_rcpumask; + ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq, &dev->kobj, "cpufreq"); if (ret) { pr_err("%s: failed to init policy->kobj: %d\n", __func__, ret); - goto err_free_rcpumask; + goto err_free_real_cpus; } INIT_LIST_HEAD(&policy->policy_list); @@ -1178,6 +1181,8 @@ static struct cpufreq_policy *cpufreq_po return policy; +err_free_real_cpus: + free_cpumask_var(policy->real_cpus); err_free_rcpumask: free_cpumask_var(policy->related_cpus); err_free_cpumask: @@ -1228,6 +1233,7 @@ static void cpufreq_policy_free(struct c write_unlock_irqrestore(&cpufreq_driver_lock, flags); cpufreq_policy_put_kobj(policy, notify); + free_cpumask_var(policy->real_cpus); free_cpumask_var(policy->related_cpus); free_cpumask_var(policy->cpus); kfree(policy); @@ -1252,14 +1258,17 @@ static int cpufreq_add_dev(struct device pr_debug("adding CPU %u\n", cpu); - /* - * Only possible if 'cpu' wasn't physically present earlier and we are - * here from subsys_interface add callback. A hotplug notifier will - * follow and we will handle it like logical CPU hotplug then. For now, - * just create the sysfs link. - */ - if (cpu_is_offline(cpu)) - return add_cpu_dev_symlink(per_cpu(cpufreq_cpu_data, cpu), cpu); + if (cpu_is_offline(cpu)) { + /* + * Only possible if we are here from the subsys_interface add + * callback. A hotplug notifier will follow and we will handle + * it as logical CPU hotplug then. For now, just create the + * sysfs link, unless there is no policy. + */ + policy = per_cpu(cpufreq_cpu_data, cpu); + return policy && !cpumask_test_and_set_cpu(cpu, policy->real_cpus) + ? add_cpu_dev_symlink(policy, cpu) : 0; + } if (!down_read_trylock(&cpufreq_rwsem)) return 0; @@ -1301,6 +1310,9 @@ static int cpufreq_add_dev(struct device /* related cpus should atleast have policy->cpus */ cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus); + cpumask_and(policy->cpus, policy->cpus, cpu_present_mask); + cpumask_or(policy->real_cpus, policy->real_cpus, policy->cpus); + /* * affected cpus must always be the one, which are online. We aren't * managing offline cpus here. @@ -1525,19 +1537,16 @@ static int cpufreq_remove_dev(struct dev * link or free policy here. */ if (cpu_is_offline(cpu)) { - struct cpumask mask; - if (!policy) return 0; - cpumask_copy(&mask, policy->related_cpus); - cpumask_clear_cpu(cpu, &mask); + cpumask_clear_cpu(cpu, policy->real_cpus); /* * Free policy only if all policy->related_cpus are removed * physically. */ - if (cpumask_intersects(&mask, cpu_present_mask)) { + if (!cpumask_empty(policy->real_cpus)) { remove_cpu_dev_symlink(policy, cpu); return 0; }