From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755355AbaKEO70 (ORCPT ); Wed, 5 Nov 2014 09:59:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37974 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755348AbaKEOyT (ORCPT ); Wed, 5 Nov 2014 09:54:19 -0500 From: Prarit Bhargava To: linux-kernel@vger.kernel.org Cc: robert.schoene@tu-dresden.de, sboyd@codeaurora.org, Prarit Bhargava , "Rafael J. Wysocki" , Viresh Kumar , linux-pm@vger.kernel.org Subject: [PATCH 3/5] cpufreq, dbs_data->usage count must be atomic Date: Wed, 5 Nov 2014 09:53:57 -0500 Message-Id: <1415199239-19019-4-git-send-email-prarit@redhat.com> In-Reply-To: <1415199239-19019-1-git-send-email-prarit@redhat.com> References: <1415199239-19019-1-git-send-email-prarit@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The usage_count value can be modified from several cpus concurrently if !CPUFREQ_HAVE_GOVERNOR_PER_POLICY. This leads to a variety of panics in which the usage_count is negative or exceeds the number of cpus in the system. It must be switched to atomic_t and protected with a mutex to make sure that future read/writes obtain the correct data. Cc: "Rafael J. Wysocki" Cc: Viresh Kumar Cc: linux-pm@vger.kernel.org Signed-off-by: Prarit Bhargava --- drivers/cpufreq/cpufreq_governor.c | 16 ++++++++++++---- drivers/cpufreq/cpufreq_governor.h | 3 ++- 2 files changed, 14 insertions(+), 5 deletions(-) diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index 1b44496..32ad9db 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -265,7 +265,9 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, if (have_governor_per_policy()) { WARN_ON(dbs_data); } else if (dbs_data) { - dbs_data->usage_count++; + mutex_lock(&dbs_data->usage_count_mutex); + atomic_inc(&dbs_data->usage_count); + mutex_unlock(&dbs_data->usage_count_mutex); policy->governor_data = dbs_data; return 0; } @@ -277,7 +279,10 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, } dbs_data->cdata = cdata; - dbs_data->usage_count = 1; + mutex_init(&dbs_data->usage_count_mutex); + mutex_lock(&dbs_data->usage_count_mutex); + atomic_set(&dbs_data->usage_count, 1); + mutex_unlock(&dbs_data->usage_count_mutex); rc = cdata->init(dbs_data); if (rc) { pr_err("%s: POLICY_INIT: init() failed\n", __func__); @@ -322,7 +327,8 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, return 0; case CPUFREQ_GOV_POLICY_EXIT: - if (!--dbs_data->usage_count) { + mutex_lock(&dbs_data->usage_count_mutex); + if (atomic_dec_and_test(&dbs_data->usage_count)) { sysfs_remove_group(get_governor_parent_kobj(policy), get_sysfs_attr(dbs_data)); @@ -338,9 +344,11 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, } cdata->exit(dbs_data); + mutex_unlock(&dbs_data->usage_count_mutex); kfree(dbs_data); cdata->gdbs_data = NULL; - } + } else + mutex_unlock(&dbs_data->usage_count_mutex); policy->governor_data = NULL; return 0; diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h index cc401d1..53ca449 100644 --- a/drivers/cpufreq/cpufreq_governor.h +++ b/drivers/cpufreq/cpufreq_governor.h @@ -219,7 +219,8 @@ struct common_dbs_data { struct dbs_data { struct common_dbs_data *cdata; unsigned int min_sampling_rate; - int usage_count; + struct mutex usage_count_mutex; + atomic_t usage_count; void *tuners; /* dbs_mutex protects dbs_enable in governor start/stop */ -- 1.7.9.3