cpufreq: unlock correct rwsem while updating policy->cpu (8efd5765) · Commits · 戴 / test

Current code looks like this: WARN_ON(lock_policy_rwsem_write(cpu)); update_policy_cpu(policy, new_cpu); unlock_policy_rwsem_write(cpu); {lock|unlock}_policy_rwsem_write(cpu) takes/releases policy->cpu's rwsem. Because cpu is changing with the call to update_policy_cpu(), the unlock_policy_rwsem_write() will release the incorrect lock. The right solution would be to release the same lock as was taken earlier. Also update_policy_cpu() was also called from cpufreq_add_dev() without any locks and so its better if we move this locking to inside update_policy_cpu(). This patch fixes a regression introduced in 3.12 by commit (cpufreq: Extract the handover of policy cpu to a helper function). Reported-and-tested-by:

Jon <Medhurst<tixy@linaro.org> Signed-off-by:

Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by:

Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -952,9 +952,20 @@ static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
		if (cpu == policy->cpu)
		return;

		/*
		* Take direct locks as lock_policy_rwsem_write wouldn't work here.
		* Also lock for last cpu is enough here as contention will happen only
		* after policy->cpu is changed and after it is changed, other threads
		* will try to acquire lock for new cpu. And policy is already updated
		* by then.
		*/
		down_write(&per_cpu(cpu_policy_rwsem, policy->cpu));

		policy->last_cpu = policy->cpu;
		policy->cpu = cpu;

		up_write(&per_cpu(cpu_policy_rwsem, policy->last_cpu));

		#ifdef CONFIG_CPU_FREQ_TABLE
		cpufreq_frequency_table_update_policy_cpu(policy);
		#endif
		@@ -1200,9 +1211,7 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,

		new_cpu = cpufreq_nominate_new_policy_cpu(policy, cpu, frozen);
		if (new_cpu >= 0) {
		WARN_ON(lock_policy_rwsem_write(cpu));
		update_policy_cpu(policy, new_cpu);
		unlock_policy_rwsem_write(cpu);

		if (!frozen) {
		pr_debug("%s: policy Kobject moved to cpu: %d "

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