cpufreq: Clear policy->cpus bits in __cpufreq_remove_dev_finish()

This broke after a recent change "cedb70af cpufreq: Split __cpufreq_remove_dev()
into two parts" from Srivatsa.

Consider a scenario where we have two CPUs in a policy (0 & 1) and we are
removing CPU 1. On the call to __cpufreq_remove_dev_prepare() we have cleared 1
from policy->cpus and now on a call to __cpufreq_remove_dev_finish() we read
cpumask_weight of policy->cpus, which will come as 1 and this code will behave
as if we are removing the last CPU from policy :)

Fix it by clearing the CPU mask in __cpufreq_remove_dev_finish() instead of
__cpufreq_remove_dev_prepare().
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -1125,7 +1125,7 @@ static int cpufreq_nominate_new_policy_cpu(struct cpufreq_policy *policy,
 	int ret;
 
 	/* first sibling now owns the new sysfs dir */
-	cpu_dev = get_cpu_device(cpumask_first(policy->cpus));
+	cpu_dev = get_cpu_device(cpumask_any_but(policy->cpus, old_cpu));
 
 	/* Don't touch sysfs files during light-weight tear-down */
 	if (frozen)
@@ -1189,12 +1189,9 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
 			policy->governor->name, CPUFREQ_NAME_LEN);
 #endif
 
-	WARN_ON(lock_policy_rwsem_write(cpu));
+	lock_policy_rwsem_read(cpu);
 	cpus = cpumask_weight(policy->cpus);
-
-	if (cpus > 1)
-		cpumask_clear_cpu(cpu, policy->cpus);
-	unlock_policy_rwsem_write(cpu);
+	unlock_policy_rwsem_read(cpu);
 
 	if (cpu != policy->cpu) {
 		if (!frozen)
@@ -1237,9 +1234,12 @@ static int __cpufreq_remove_dev_finish(struct device *dev,
 		return -EINVAL;
 	}
 
-	lock_policy_rwsem_read(cpu);
+	WARN_ON(lock_policy_rwsem_write(cpu));
 	cpus = cpumask_weight(policy->cpus);
-	unlock_policy_rwsem_read(cpu);
+
+	if (cpus > 1)
+		cpumask_clear_cpu(cpu, policy->cpus);
+	unlock_policy_rwsem_write(cpu);
 
 	/* If cpu is last user of policy, free policy */
 	if (cpus == 1) {