cpufreq: Do not hold driver module references for additional policy CPUs

The cpufreq core is a little inconsistent in the way it uses the
driver module refcount.

Namely, if __cpufreq_add_dev() is called for a CPU that doesn't
share the policy object with any other CPUs, the driver module
refcount it grabs to start with will be dropped by it before
returning and will be equal to whatever it had been before that
function was invoked.

However, if the given CPU does share the policy object with other
CPUs, either cpufreq_add_policy_cpu() is called to link the new CPU
to the existing policy, or cpufreq_add_dev_symlink() is used to link
the other CPUs sharing the policy with it to the just created policy
object.  In that case, because both cpufreq_add_policy_cpu() and
cpufreq_add_dev_symlink() call cpufreq_cpu_get() for the given
policy (the latter possibly many times) without the balancing
cpufreq_cpu_put() (unless there is an error), the driver module
refcount will be left by __cpufreq_add_dev() with a nonzero value
(different from the initial one).

To remove that inconsistency make cpufreq_add_policy_cpu() execute
cpufreq_cpu_put() for the given policy before returning, which
decrements the driver module refcount so that it will be equal to its
initial value after __cpufreq_add_dev() returns.  Also remove the
cpufreq_cpu_get() call from cpufreq_add_dev_symlink(), since both the
policy refcount and the driver module refcount are nonzero when it is
called and they don't need to be bumped up by it.

Accordingly, drop the cpufreq_cpu_put() from __cpufreq_remove_dev(),
since it is only necessary to balance the cpufreq_cpu_get() called
by cpufreq_add_policy_cpu() or cpufreq_add_dev_symlink().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

1 files changed, 7 insertions, 21 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 576b312645a..c8b2ca0f44a 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -818,14 +818,11 @@ static int cpufreq_add_dev_symlink(struct cpufreq_policy *policy)
 			continue;
 
 		pr_debug("Adding link for CPU: %u\n", j);
-		cpufreq_cpu_get(policy->cpu);
 		cpu_dev = get_cpu_device(j);
 		ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj,
 					"cpufreq");
-		if (ret) {
-			cpufreq_cpu_put(policy);
-			return ret;
-		}
+		if (ret)
+			break;
 	}
 	return ret;
 }
@@ -908,7 +905,8 @@ static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
 	unsigned long flags;
 
 	policy = cpufreq_cpu_get(sibling);
-	WARN_ON(!policy);
+	if (WARN_ON_ONCE(!policy))
+		return -ENODATA;
 
 	if (has_target)
 		__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
@@ -930,16 +928,10 @@ static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
 	}
 
 	/* Don't touch sysfs links during light-weight init */
-	if (frozen) {
-		/* Drop the extra refcount that we took above */
-		cpufreq_cpu_put(policy);
-		return 0;
-	}
-
-	ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
-	if (ret)
-		cpufreq_cpu_put(policy);
+	if (!frozen)
+		ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
 
+	cpufreq_cpu_put(policy);
 	return ret;
 }
 #endif
@@ -1298,12 +1290,6 @@ static int __cpufreq_remove_dev(struct device *dev,
 		if (!frozen)
 			cpufreq_policy_free(data);
 	} else {
-
-		if (!frozen) {
-			pr_debug("%s: removing link, cpu: %d\n", __func__, cpu);
-			cpufreq_cpu_put(data);
-		}
-
 		if (cpufreq_driver->target) {
 			__cpufreq_governor(data, CPUFREQ_GOV_START);
 			__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);