Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Subject | [PATCH] cpufreq: Avoid using inactive policies | Date | Thu, 17 Nov 2016 16:08:25 +0100 |
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.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 the policy 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@intel.com> --- drivers/cpufreq/cpufreq.c | 8 +++++++- 1 file changed, 7 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 +2268,9 @@ int cpufreq_update_policy(unsigned int c down_write(&policy->rwsem); + if (policy_is_inactive(policy)) + 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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