[CPUFREQ] core: CPUFREQ_GOV_STOP needs to be last

Assert that the call to the cpufreq governor with CPUFREQ_GOV_STOP is really
the last. Without this patch, some strange in-kernel preemption combined with
the scheduler disliking the "removing" task may cause the opposite.
Signed-off-by: Dominik Brodowski <linux@brodo.de>
Signed-off-by: Dave Jones <davej@redhat.com>

drivers/cpufreq/cpufreq.c

@@ -763,8 +763,11 @@ static int cpufreq_remove_dev (struct sys_device * sys_dev)
 	spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
 #endif
 
+	down(&data->lock);
 	if (cpufreq_driver->target)
 		__cpufreq_governor(data, CPUFREQ_GOV_STOP);
+	cpufreq_driver->target = NULL;
+	up(&data->lock);
 
 	kobject_unregister(&data->kobj);
 
@@ -1025,7 +1028,7 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
 	lock_cpu_hotplug();
 	dprintk("target for CPU %u: %u kHz, relation %u\n", policy->cpu,
 		target_freq, relation);
-	if (cpu_online(policy->cpu))
+	if (cpu_online(policy->cpu) && cpufreq_driver->target)
 		retval = cpufreq_driver->target(policy, target_freq, relation);
 	unlock_cpu_hotplug();
 	return retval;