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Subject[PATCH 5/5] cpufreq: Simplify cpufreq_add_dev()
Date
Currently cpufreq_add_dev() firsts allocates policy, calls driver->init() and
then checks if this cpu is already managed or not. And if it is already managed,
free its policy.

We can save all this if we somehow know cpu is managed or not in advance.
policy->related_cpus contains list of all valid sibling cpus of policy->cpu. We
can check this to know if current cpu is already managed.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
---
drivers/cpufreq/cpufreq.c | 150 ++++++++++++++++------------------------------
1 file changed, 52 insertions(+), 98 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index f1bab33..bf02a3e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -703,92 +703,6 @@ static struct kobj_type ktype_cpufreq = {
.release = cpufreq_sysfs_release,
};

-/*
- * Returns:
- * Negative: Failure
- * 0: Success
- * Positive: When we have a managed CPU and the sysfs got symlinked
- */
-static int cpufreq_add_dev_policy(unsigned int cpu,
- struct cpufreq_policy *policy,
- struct device *dev)
-{
- int ret = 0;
-#ifdef CONFIG_SMP
- unsigned long flags;
- unsigned int j;
-#ifdef CONFIG_HOTPLUG_CPU
- struct cpufreq_governor *gov;
-
- gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
- if (gov) {
- policy->governor = gov;
- pr_debug("Restoring governor %s for cpu %d\n",
- policy->governor->name, cpu);
- }
-#endif
-
- for_each_cpu(j, policy->cpus) {
- struct cpufreq_policy *managed_policy;
-
- if (cpu == j)
- continue;
-
- /* Check for existing affected CPUs.
- * They may not be aware of it due to CPU Hotplug.
- * cpufreq_cpu_put is called when the device is removed
- * in __cpufreq_remove_dev()
- */
- managed_policy = cpufreq_cpu_get(j);
- if (unlikely(managed_policy)) {
-
- /* Set proper policy_cpu */
- unlock_policy_rwsem_write(cpu);
- per_cpu(cpufreq_policy_cpu, cpu) = managed_policy->cpu;
-
- if (lock_policy_rwsem_write(cpu) < 0) {
- /* Should not go through policy unlock path */
- if (cpufreq_driver->exit)
- cpufreq_driver->exit(policy);
- cpufreq_cpu_put(managed_policy);
- return -EBUSY;
- }
-
- __cpufreq_governor(managed_policy, CPUFREQ_GOV_STOP);
-
- spin_lock_irqsave(&cpufreq_driver_lock, flags);
- cpumask_copy(managed_policy->cpus, policy->cpus);
- per_cpu(cpufreq_cpu_data, cpu) = managed_policy;
- spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
-
- __cpufreq_governor(managed_policy, CPUFREQ_GOV_START);
- __cpufreq_governor(managed_policy, CPUFREQ_GOV_LIMITS);
-
- pr_debug("CPU already managed, adding link\n");
- ret = sysfs_create_link(&dev->kobj,
- &managed_policy->kobj,
- "cpufreq");
- if (ret)
- cpufreq_cpu_put(managed_policy);
- /*
- * Success. We only needed to be added to the mask.
- * Call driver->exit() because only the cpu parent of
- * the kobj needed to call init().
- */
- if (cpufreq_driver->exit)
- cpufreq_driver->exit(policy);
-
- if (!ret)
- return 1;
- else
- return ret;
- }
- }
-#endif
- return ret;
-}
-
-
/* symlink affected CPUs */
static int cpufreq_add_dev_symlink(unsigned int cpu,
struct cpufreq_policy *policy)
@@ -893,6 +807,41 @@ err_out_kobj_put:
return ret;
}

+static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
+ struct device *dev)
+{
+ struct cpufreq_policy *policy;
+ int ret = 0;
+ unsigned long flags;
+
+ policy = cpufreq_cpu_get(sibling);
+ WARN_ON(!policy);
+
+ per_cpu(cpufreq_policy_cpu, cpu) = policy->cpu;
+
+ lock_policy_rwsem_write(cpu);
+
+ __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+
+ spin_lock_irqsave(&cpufreq_driver_lock, flags);
+ cpumask_set_cpu(cpu, policy->cpus);
+ per_cpu(cpufreq_cpu_data, cpu) = policy;
+ spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+
+ __cpufreq_governor(policy, CPUFREQ_GOV_START);
+ __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+
+ unlock_policy_rwsem_write(cpu);
+
+ ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
+ if (ret) {
+ cpufreq_cpu_put(policy);
+ return ret;
+ }
+
+ return 0;
+}
+

/**
* cpufreq_add_dev - add a CPU device
@@ -905,12 +854,12 @@ err_out_kobj_put:
*/
static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
{
- unsigned int cpu = dev->id;
- int ret = 0, found = 0;
+ unsigned int j, cpu = dev->id;
+ int ret = -ENOMEM, found = 0;
struct cpufreq_policy *policy;
unsigned long flags;
- unsigned int j;
#ifdef CONFIG_HOTPLUG_CPU
+ struct cpufreq_governor *gov;
int sibling;
#endif

@@ -927,6 +876,13 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
cpufreq_cpu_put(policy);
return 0;
}
+
+ /* Check if this cpu was hot-unplugged earlier and has siblings */
+ for_each_online_cpu(sibling) {
+ struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
+ if (cp && cpumask_test_cpu(cpu, cp->related_cpus))
+ return cpufreq_add_policy_cpu(cpu, sibling, dev);
+ }
#endif

if (!try_module_get(cpufreq_driver->owner)) {
@@ -934,7 +890,6 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
goto module_out;
}

- ret = -ENOMEM;
policy = kzalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
if (!policy)
goto nomem_out;
@@ -992,14 +947,14 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
CPUFREQ_START, policy);

- ret = cpufreq_add_dev_policy(cpu, policy, dev);
- if (ret) {
- if (ret > 0)
- /* This is a managed cpu, symlink created,
- exit with 0 */
- ret = 0;
- goto err_unlock_policy;
+#ifdef CONFIG_HOTPLUG_CPU
+ gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
+ if (gov) {
+ policy->governor = gov;
+ pr_debug("Restoring governor %s for cpu %d\n",
+ policy->governor->name, cpu);
}
+#endif

ret = cpufreq_add_dev_interface(cpu, policy, dev);
if (ret)
@@ -1013,7 +968,6 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)

return 0;

-
err_out_unregister:
spin_lock_irqsave(&cpufreq_driver_lock, flags);
for_each_cpu(j, policy->cpus)
--
1.7.12.rc2.18.g61b472e


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