From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756095AbcBCOCz (ORCPT ); Wed, 3 Feb 2016 09:02:55 -0500 Received: from mail-pa0-f43.google.com ([209.85.220.43]:35383 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756011AbcBCOCt (ORCPT ); Wed, 3 Feb 2016 09:02:49 -0500 From: Viresh Kumar To: Rafael Wysocki , juri.lelli@arm.com Cc: linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, skannan@codeaurora.org, peterz@infradead.org, mturquette@baylibre.com, steve.muckle@linaro.org, vincent.guittot@linaro.org, morten.rasmussen@arm.com, dietmar.eggemann@arm.com, linux-kernel@vger.kernel.org, Viresh Kumar Subject: [PATCH V2 6/7] cpufreq: Call __cpufreq_governor() with policy->rwsem held Date: Wed, 3 Feb 2016 19:32:22 +0530 Message-Id: X-Mailer: git-send-email 2.7.0.79.gdc08a19 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This isn't followed properly by all parts of the core code, some follow it, whereas others don't. Enforcing it will also enable us to remove cpufreq_governor_lock, that is used today because we can't guarantee that __cpufreq_governor() isn't executed in parallel. We should also ensure that the lock is held across state changes to the governors. For example, while adding a CPU to the policy on cpu-online path, we need to stop the governor, change policy->cpus, start the governor and then refresh its limits. The complete sequence must be guaranteed to execute without any concurrent races. And that can be achieved using policy->rwsem around these use cases. Also note that cpufreq_driver->stop_cpu() and ->exit() can get called while policy->rwsem is held. That shouldn't have any side effects though. Signed-off-by: Viresh Kumar --- drivers/cpufreq/cpufreq.c | 45 ++++++++++++++++++++++++++++++--------------- 1 file changed, 30 insertions(+), 15 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index dc43294e7b31..4fc3889ca7c9 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -996,30 +996,29 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp if (cpumask_test_cpu(cpu, policy->cpus)) return 0; + down_write(&policy->rwsem); if (has_target()) { ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP); if (ret) { pr_err("%s: Failed to stop governor\n", __func__); - return ret; + goto unlock; } } - down_write(&policy->rwsem); cpumask_set_cpu(cpu, policy->cpus); - up_write(&policy->rwsem); if (has_target()) { ret = __cpufreq_governor(policy, CPUFREQ_GOV_START); if (!ret) ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); - if (ret) { + if (ret) pr_err("%s: Failed to start governor\n", __func__); - return ret; - } } - return 0; +unlock: + up_write(&policy->rwsem); + return ret; } static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu) @@ -1322,13 +1321,13 @@ static void cpufreq_offline(unsigned int cpu) return; } + down_write(&policy->rwsem); if (has_target()) { ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP); if (ret) pr_err("%s: Failed to stop governor\n", __func__); } - down_write(&policy->rwsem); cpumask_clear_cpu(cpu, policy->cpus); if (policy_is_inactive(policy)) { @@ -1341,7 +1340,6 @@ static void cpufreq_offline(unsigned int cpu) /* Nominate new CPU */ policy->cpu = cpumask_any(policy->cpus); } - up_write(&policy->rwsem); /* Start governor again for active policy */ if (!policy_is_inactive(policy)) { @@ -1376,6 +1374,7 @@ static void cpufreq_offline(unsigned int cpu) cpufreq_driver->exit(policy); policy->freq_table = NULL; } + up_write(&policy->rwsem); } /** @@ -1572,6 +1571,7 @@ EXPORT_SYMBOL(cpufreq_generic_suspend); void cpufreq_suspend(void) { struct cpufreq_policy *policy; + int ret; if (!cpufreq_driver) return; @@ -1582,7 +1582,11 @@ void cpufreq_suspend(void) pr_debug("%s: Suspending Governors\n", __func__); for_each_active_policy(policy) { - if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP)) + down_write(&policy->rwsem); + ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP); + up_write(&policy->rwsem); + + if (ret) pr_err("%s: Failed to stop governor for policy: %p\n", __func__, policy); else if (cpufreq_driver->suspend @@ -1604,6 +1608,7 @@ void cpufreq_suspend(void) void cpufreq_resume(void) { struct cpufreq_policy *policy; + int ret; if (!cpufreq_driver) return; @@ -1616,13 +1621,20 @@ void cpufreq_resume(void) pr_debug("%s: Resuming Governors\n", __func__); for_each_active_policy(policy) { - if (cpufreq_driver->resume && cpufreq_driver->resume(policy)) + if (cpufreq_driver->resume && cpufreq_driver->resume(policy)) { pr_err("%s: Failed to resume driver: %p\n", __func__, policy); - else if (__cpufreq_governor(policy, CPUFREQ_GOV_START) - || __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS)) - pr_err("%s: Failed to start governor for policy: %p\n", - __func__, policy); + } else { + down_write(&policy->rwsem); + ret = __cpufreq_governor(policy, CPUFREQ_GOV_START); + if (!ret) + __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); + up_write(&policy->rwsem); + + if (ret) + pr_err("%s: Failed to start governor for policy: %p\n", + __func__, policy); + } } /* @@ -2276,8 +2288,11 @@ static int cpufreq_boost_set_sw(int state) __func__); break; } + + down_write(&policy->rwsem); policy->user_policy.max = policy->max; __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); + up_write(&policy->rwsem); } } -- 2.7.0.79.gdc08a19