Commit 11e584cf authored Jun 10, 2015 by Viresh Kumar Committed by Rafael J. Wysocki Jun 10, 2015

cpufreq: Don't allow updating inactive policies from sysfs



Later commits would change the way policies are managed today. Policies
wouldn't be freed on cpu hotplug (currently they aren't freed only for
suspend), and while the CPU is offline, the sysfs cpufreq files would
still be present.

User may accidentally try to update the sysfs files in following
directory: '/sys/devices/system/cpu/cpuX/cpufreq/'. And that would
result in undefined behavior as policy wouldn't be active then.

Apart from updating the store() routine, we also update __cpufreq_get()
which can call cpufreq_out_of_sync(). The later routine tries to update
policy->cur and starts notifying kernel about it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 6c1e4591

drivers/cpufreq/cpufreq.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -875,11 +875,18 @@ static ssize_t store(struct kobject kobj, struct attribute attr,

		down_write(&policy->rwsem);

		/* Updating inactive policies is invalid, so avoid doing that. */
		if (unlikely(policy_is_inactive(policy))) {
		ret = -EBUSY;
		goto unlock_policy_rwsem;
		}

		if (fattr->store)
		ret = fattr->store(policy, buf, count);
		else
		ret = -EIO;

		unlock_policy_rwsem:
		up_write(&policy->rwsem);

		up_read(&cpufreq_rwsem);
		@@ -1610,6 +1617,10 @@ static unsigned int __cpufreq_get(struct cpufreq_policy *policy)

		ret_freq = cpufreq_driver->get(policy->cpu);

		/* Updating inactive policies is invalid, so avoid doing that. */
		if (unlikely(policy_is_inactive(policy)))
		return ret_freq;

		if (ret_freq && policy->cur &&
		!(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
		/* verify no discrepancy between actual and