Commit 6954ca9c authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki

cpufreq: Don't use cpu removed during cpufreq_driver_unregister

This is how the core works:
 - subsys_interface_unregister()
   - for_each_cpu() call cpufreq_remove_dev(), i.e. 0,1,2,3,4 when we

 - Remove policy node
 - Call cpufreq_add_dev() for next cpu, sharing mask with removed cpu.
   i.e. When cpu 0 is removed, we call it for cpu 1. And when called for cpu 2,
   we call it for cpu 3.
   - cpufreq_add_dev() would call cpufreq_driver->init()
   - init would return mask as AND of 2, 3 and 4 for cluster A7.
   - cpufreq core would do online_cpu && policy->cpus
     Here is the BUG(). Because cpu hasn't died but we have just unregistered
     the cpufreq driver, online cpu would still have cpu 2 in it. And so thing
     go bad again.

Solution: Keep cpumask of cpus that are registered with cpufreq core and clear
	  cpus when we get a call from subsys_interface_unregister() via
Signed-off-by: default avatarViresh Kumar <>
Signed-off-by: default avatarRafael J. Wysocki <>
parent f6a7409c
......@@ -47,6 +47,9 @@ static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
static DEFINE_SPINLOCK(cpufreq_driver_lock);
/* Used when we unregister cpufreq driver */
static struct cpumask cpufreq_online_mask;
* cpu_policy_rwsem is a per CPU reader-writer semaphore designed to cure
* all cpufreq/hotplug/workqueue/etc related lock issues.
......@@ -981,6 +984,7 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
* managing offline cpus here.
cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
cpumask_and(policy->cpus, policy->cpus, &cpufreq_online_mask);
policy->user_policy.min = policy->min;
policy->user_policy.max = policy->max;
......@@ -1064,7 +1068,6 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
per_cpu(cpufreq_cpu_data, cpu) = NULL;
/* if this isn't the CPU which is the parent of the kobj, we
* only need to unlink, put and exit
......@@ -1185,6 +1188,7 @@ static int cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
if (unlikely(lock_policy_rwsem_write(cpu)))
cpumask_clear_cpu(cpu, &cpufreq_online_mask);
retval = __cpufreq_remove_dev(dev, sif);
return retval;
......@@ -1903,6 +1907,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
cpufreq_driver = driver_data;
spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
ret = subsys_interface_register(&cpufreq_interface);
if (ret)
goto err_null_driver;
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