From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: [PATCH v2] cpufreq: Avoid using inactive policies Date: Fri, 18 Nov 2016 13:40:45 +0100 Message-ID: <2709142.YWmMDScDNY@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: Received: from cloudserver094114.home.net.pl ([79.96.170.134]:42407 "EHLO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752821AbcKRMdI (ORCPT ); Fri, 18 Nov 2016 07:33:08 -0500 Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Linux PM list , Viresh Kumar Cc: Linux Kernel Mailing List , Srinivas Pandruvada From: Rafael J. Wysocki There are two places in the cpufreq core in which low-level driver callbacks may be invoked for an inactive cpufreq policy, which isn't guaranteed to work in general. Both are due to possible races with CPU offline. First, in cpufreq_get(), the policy may become inactive after the check against policy->cpus in cpufreq_cpu_get() and before policy->rwsem is acquired, in which case using it going forward may not be correct. Second, an analogous situation is possible in cpufreq_update_policy(). Avoid using inactive policies by adding policy_is_inactive() checks to the code in the above places. Signed-off-by: Rafael J. Wysocki --- -> v2: Initialize ret in cpufreq_update_policy() if the inactive policy check doesn't pass. --- drivers/cpufreq/cpufreq.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) Index: linux-pm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq.c +++ linux-pm/drivers/cpufreq/cpufreq.c @@ -1526,7 +1526,10 @@ unsigned int cpufreq_get(unsigned int cp if (policy) { down_read(&policy->rwsem); - ret_freq = __cpufreq_get(policy); + + if (!policy_is_inactive(policy)) + ret_freq = __cpufreq_get(policy); + up_read(&policy->rwsem); cpufreq_cpu_put(policy); @@ -2265,6 +2268,11 @@ int cpufreq_update_policy(unsigned int c down_write(&policy->rwsem); + if (policy_is_inactive(policy)) { + ret = -ENODEV; + goto unlock; + } + pr_debug("updating policy for CPU %u\n", cpu); memcpy(&new_policy, policy, sizeof(*policy)); new_policy.min = policy->user_policy.min;