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Subject[PATCH v4 4/5] cpufreq: Properly handle physical CPU hot-add/hot-remove
Date
When CPUs are physically added/removed, its cpuX sysfs directory is
dynamically added/removed. To handle this correctly, the cpufreq sysfs
nodes also need to be added/removed dynamically.

Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
---
drivers/cpufreq/cpufreq.c | 46 +++++++++++++++++++++++++++++++++-------------
1 file changed, 33 insertions(+), 13 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d9fc6e5..97edf05 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -41,6 +41,7 @@ static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data_fallback);
static DEFINE_RWLOCK(cpufreq_driver_lock);
DEFINE_MUTEX(cpufreq_governor_lock);
static LIST_HEAD(cpufreq_policy_list);
+static cpumask_t has_symlink;

/* This one keeps track of the previously set governor of a removed CPU */
static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
@@ -865,7 +866,10 @@ static int cpufreq_add_dev_symlink(struct cpufreq_policy *policy)
unsigned int j;
int ret = 0;

- for_each_cpu(j, policy->related_cpus) {
+ /* Only some of the related CPUs might be present. So, create
+ * symlinks only for those.
+ */
+ for_each_cpu_and(j, policy->related_cpus, cpu_present_mask) {
struct device *cpu_dev;

if (j == policy->kobj_cpu)
@@ -877,6 +881,7 @@ static int cpufreq_add_dev_symlink(struct cpufreq_policy *policy)
"cpufreq");
if (ret)
break;
+ cpumask_set_cpu(j, &has_symlink);
}
return ret;
}
@@ -1101,9 +1106,6 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
unsigned long flags;
bool recover_policy = cpufreq_suspended;

- if (cpu_is_offline(cpu))
- return 0;
-
pr_debug("adding CPU %u\n", cpu);

#ifdef CONFIG_SMP
@@ -1111,7 +1113,19 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
* CPU because it is in the same boat. */
policy = cpufreq_cpu_get(cpu);
if (policy) {
- if (!cpumask_test_cpu(cpu, policy->cpus))
+ /* If a CPU gets physically plugged in after one or more of
+ * its related CPUs are ONLINE, we need to create a symlink
+ * for it since it wouldn't have been created when the policy
+ * was initialized. Do this as soon as it's plugged in.
+ */
+ if (sif && !cpumask_test_cpu(cpu, &has_symlink)) {
+ ret = sysfs_create_link(&dev->kobj, &policy->kobj,
+ "cpufreq");
+ if (!ret)
+ cpumask_set_cpu(cpu, &has_symlink);
+ }
+
+ if (!cpumask_test_cpu(cpu, policy->cpus) && cpu_online(cpu))
ret = cpufreq_add_policy_cpu(policy, cpu, dev);
else
ret = 0;
@@ -1120,6 +1134,9 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
}
#endif

+ if (cpu_is_offline(cpu))
+ return 0;
+
if (!down_read_trylock(&cpufreq_rwsem))
return 0;

@@ -1303,25 +1320,24 @@ static int cpufreq_nominate_new_policy_cpu(struct cpufreq_policy *policy,
unsigned int old_cpu)
{
struct device *cpu_dev;
+ unsigned int new_cpu;
int ret;

/* first sibling now owns the new sysfs dir */
- cpu_dev = get_cpu_device(cpumask_any_but(policy->cpus, old_cpu));
+ for_each_cpu_and(new_cpu, policy->related_cpus, cpu_present_mask)
+ if (new_cpu != old_cpu)
+ break;
+ cpu_dev = get_cpu_device(new_cpu);

sysfs_remove_link(&cpu_dev->kobj, "cpufreq");
ret = kobject_move(&policy->kobj, &cpu_dev->kobj);
if (ret) {
pr_err("%s: Failed to move kobj: %d\n", __func__, ret);
-
- down_write(&policy->rwsem);
- cpumask_set_cpu(old_cpu, policy->cpus);
- up_write(&policy->rwsem);
-
ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj,
"cpufreq");
-
return -EINVAL;
}
+ cpumask_clear_cpu(new_cpu, &has_symlink);
policy->kobj_cpu = cpu_dev->id;

return cpu_dev->id;
@@ -1407,8 +1423,12 @@ static int __cpufreq_remove_dev_finish(struct device *dev,
cpus = cpumask_weight(policy->cpus);
up_read(&policy->rwsem);

- if (cpu != policy->kobj_cpu)
+ if (cpu != policy->kobj_cpu) {
sysfs_remove_link(&dev->kobj, "cpufreq");
+ cpumask_clear_cpu(cpu, &has_symlink);
+ } else {
+ cpufreq_nominate_new_policy_cpu(policy, cpu);
+ }

/* If cpu is last user of policy, free policy */
if (cpus == 0) {
--
1.8.2.1
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