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))
+ goto unlock;
+
pr_debug("updating policy for CPU %u\n", cpu);
memcpy(&new_policy, policy, sizeof(*policy));
new_policy.min = policy->user_policy.min;
