Commit e660a2e6 authored May 11, 2022 by Rafael J. Wysocki Committed by Greg Kroah-Hartman Jun 16, 2024

cpufreq: Rearrange locking in cpufreq_remove_dev()



[ Upstream commit f339f3541701d824a0256ad4bf14c26ceb6d79c3 ]

Currently, cpufreq_remove_dev() invokes the ->exit() driver callback
without holding the policy rwsem which is inconsistent with what
happens if ->exit() is invoked directly from cpufreq_offline().

It also manipulates the real_cpus mask and removes the CPU device
symlink without holding the policy rwsem, but cpufreq_offline() holds
the rwsem around the modifications thereof.

For consistency, modify cpufreq_remove_dev() to hold the policy rwsem
until the ->exit() callback has been called (or it has been determined
that it is not necessary to call it).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Stable-dep-of: b8f85833c057 ("cpufreq: exit() callback is optional")
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 14bef1ad

drivers/cpufreq/cpufreq.c

+14 −7

Original line number	Diff line number	Diff line
		@@ -1639,20 +1639,27 @@ static void cpufreq_remove_dev(struct device dev, struct subsys_interface sif)
		if (!policy)
		return;

		down_write(&policy->rwsem);

		if (cpu_online(cpu))
		cpufreq_offline(cpu);
		__cpufreq_offline(cpu, policy);

		cpumask_clear_cpu(cpu, policy->real_cpus);
		remove_cpu_dev_symlink(policy, dev);

		if (cpumask_empty(policy->real_cpus)) {
		if (!cpumask_empty(policy->real_cpus)) {
		up_write(&policy->rwsem);
		return;
		}

		/* We did light-weight exit earlier, do full tear down now */
		if (cpufreq_driver->offline)
		cpufreq_driver->exit(policy);

		up_write(&policy->rwsem);

		cpufreq_policy_free(policy);
		}
		}

		/**
		* cpufreq_out_of_sync - If actual and saved CPU frequency differs, we're