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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-11-18 15:40:45 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-11-21 16:35:42 +0300
commit182e36af0663a1050c42d234a5bf36f084f8c28b (patch)
tree9086484c063bb504ae0c56925ab3ceb192922581 /drivers/cpufreq
parent001c76f05b01cc8ceb2098c9ff5de2609bec7f76 (diff)
downloadlinux-182e36af0663a1050c42d234a5bf36f084f8c28b.tar.xz
cpufreq: Avoid using inactive policies
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@intel.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/cpufreq.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 6e6c1fb60fbc..ad3b319486bd 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1526,7 +1526,10 @@ unsigned int cpufreq_get(unsigned int cpu)
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 cpu)
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;