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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81182C41513 for ; Wed, 16 Aug 2023 13:07:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245364AbjHPNHN (ORCPT ); Wed, 16 Aug 2023 09:07:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245369AbjHPNGl (ORCPT ); Wed, 16 Aug 2023 09:06:41 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 871D91BFB; Wed, 16 Aug 2023 06:06:39 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6750CD75; Wed, 16 Aug 2023 06:07:20 -0700 (PDT) Received: from [192.168.178.38] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 568C33F6C4; Wed, 16 Aug 2023 06:06:36 -0700 (PDT) Message-ID: Date: Wed, 16 Aug 2023 15:06:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v3 09/12] PM: EM: Add RCU mechanism which safely cleans the old data Content-Language: en-US To: Lukasz Luba , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rafael@kernel.org Cc: rui.zhang@intel.com, amit.kucheria@verdurent.com, amit.kachhap@gmail.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, len.brown@intel.com, pavel@ucw.cz, Pierre.Gondois@arm.com, ionela.voinescu@arm.com, mhiramat@kernel.org References: <20230721155022.2339982-1-lukasz.luba@arm.com> <20230721155022.2339982-10-lukasz.luba@arm.com> From: Dietmar Eggemann In-Reply-To: <20230721155022.2339982-10-lukasz.luba@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/07/2023 17:50, Lukasz Luba wrote: > The EM is going to support runtime modifications of the power data. > Introduce RCU safe mechanism to clean up the old allocated EM data. > It also adds a mutex for the EM structure to serialize the modifiers. > > Signed-off-by: Lukasz Luba > --- > kernel/power/energy_model.c | 42 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c > index c2f8a0046f8a..4596bfe7398e 100644 > --- a/kernel/power/energy_model.c > +++ b/kernel/power/energy_model.c > @@ -23,6 +23,9 @@ > */ > static DEFINE_MUTEX(em_pd_mutex); > > +static void em_cpufreq_update_efficiencies(struct device *dev, > + struct em_perf_state *table); > + > static bool _is_cpu_device(struct device *dev) > { > return (dev->bus == &cpu_subsys); > @@ -104,6 +107,45 @@ static void em_debug_create_pd(struct device *dev) {} > static void em_debug_remove_pd(struct device *dev) {} > #endif > > +static void em_destroy_rt_table_rcu(struct rcu_head *rp) > +{ > + struct em_perf_table *runtime_table; > + > + runtime_table = container_of(rp, struct em_perf_table, rcu); > + kfree(runtime_table->state); > + kfree(runtime_table); > +} > + > +static void em_destroy_tmp_setup_rcu(struct rcu_head *rp) > +{ > + struct em_perf_table *runtime_table; > + > + runtime_table = container_of(rp, struct em_perf_table, rcu); > + kfree(runtime_table); > +} Still don't like that we have to have 2 rcu callbacks here. In case we could assign default_table to runtime_table in em_create_pd() (and not just default_table->state to runtime_table->state) IMHO we would only need one rcu callback? -->8-- -static void em_destroy_tmp_setup_rcu(struct rcu_head *rp) -{ - struct em_perf_table *runtime_table; - - runtime_table = container_of(rp, struct em_perf_table, rcu); - kfree(runtime_table); -} - static void em_perf_runtime_table_set(struct device *dev, struct em_perf_table *runtime_table) { @@ -136,13 +128,8 @@ static void em_perf_runtime_table_set(struct device *dev, em_cpufreq_update_efficiencies(dev, runtime_table->state); - /* - * Check if the 'state' array is not actually the one from setup. - * If it is then don't free it. - */ - if (tmp->state == pd->default_table->state) - call_rcu(&tmp->rcu, em_destroy_tmp_setup_rcu); - else + /* Don't free default table (inital value of runtime table) */ + if (tmp != pd->default_table) call_rcu(&tmp->rcu, em_destroy_rt_table_rcu); } @@ -349,7 +336,6 @@ static int em_create_pd(struct device *dev, int nr_states, unsigned long flags) { struct em_perf_table *default_table; - struct em_perf_table *runtime_table; struct em_perf_domain *pd; struct device *cpu_dev; int cpu, ret, num_cpus; @@ -382,24 +368,15 @@ static int em_create_pd(struct device *dev, int nr_states, pd->default_table = default_table; - runtime_table = kzalloc(sizeof(*runtime_table), GFP_KERNEL); - if (!runtime_table) { - kfree(default_table); - kfree(pd); - return -ENOMEM; - } - ret = em_create_perf_table(dev, pd, nr_states, cb, flags); if (ret) { kfree(default_table); - kfree(runtime_table); kfree(pd); return ret; } - /* Re-use temporally (till 1st modification) the memory */ - runtime_table->state = default_table->state; - rcu_assign_pointer(pd->runtime_table, runtime_table); + /* Initialize runtime table as default table */ + rcu_assign_pointer(pd->runtime_table, default_table); if (_is_cpu_device(dev)) for_each_cpu(cpu, cpus) {