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Date: Fri, 18 Nov 2016 13:40:45 +0100 From: "Rafael J. Wysocki" <rjw@...ysocki.net> To: Linux PM list <linux-pm@...r.kernel.org>, Viresh Kumar <viresh.kumar@...aro.org> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> Subject: [PATCH v2] cpufreq: Avoid using inactive policies From: Rafael J. Wysocki <rafael.j.wysocki@...el.com> 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 <rafael.j.wysocki@...el.com> --- -> 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;
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