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Subject[PATCH] cpufreq: Lock CPU online/offline in cpufreq_register_driver()
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

To protect against races with concurrent CPU online/offline, call
get_online_cpus() before registering a cpufreq driver.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpufreq/cpufreq.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -2471,10 +2471,14 @@ int cpufreq_register_driver(struct cpufr

pr_debug("trying to register driver %s\n", driver_data->name);

+ /* Protect against concurrent CPU online/offline. */
+ get_online_cpus();
+
write_lock_irqsave(&cpufreq_driver_lock, flags);
if (cpufreq_driver) {
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
- return -EEXIST;
+ ret = -EEXIST;
+ goto out;
}
cpufreq_driver = driver_data;
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
@@ -2513,7 +2517,10 @@ int cpufreq_register_driver(struct cpufr
register_hotcpu_notifier(&cpufreq_cpu_notifier);
pr_debug("driver %s up and running\n", driver_data->name);

- return 0;
+out:
+ put_online_cpus();
+ return ret;
+
err_if_unreg:
subsys_interface_unregister(&cpufreq_interface);
err_boost_unreg:
@@ -2523,7 +2530,7 @@ err_null_driver:
write_lock_irqsave(&cpufreq_driver_lock, flags);
cpufreq_driver = NULL;
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
- return ret;
+ goto out;
}
EXPORT_SYMBOL_GPL(cpufreq_register_driver);



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