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Subject[PATCH v1 3/3] cpufreq: Rearrange locking in cpufreq_remove_dev()
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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>
---
drivers/cpufreq/cpufreq.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)

Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1659,19 +1659,26 @@ static void cpufreq_remove_dev(struct de
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)) {
- /* We did light-weight exit earlier, do full tear down now */
- if (cpufreq_driver->offline)
- cpufreq_driver->exit(policy);
-
- cpufreq_policy_free(policy);
+ 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);
}

/**


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