On 17-11-16, 16:08, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wyso...@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.wyso...@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))
You also need to set some value to 'ret' as it is uninitialized right now.
> + goto unlock;
> +
> pr_debug("updating policy for CPU %u\n", cpu);
> memcpy(&new_policy, policy, sizeof(*policy));
> new_policy.min = policy->user_policy.min;
--
viresh
