[PATCH v4 1/7] cpufreq: sched: Helpers to add and remove update_util hooks

Rafael J. Wysocki
2016-03-16T15:01:46Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Replace the single helper for adding and removing cpufreq utilization
update hooks, cpufreq_set_update_util_data(), with a pair of helpers,
cpufreq_add_update_util_hook() and cpufreq_remove_update_util_hook(),
and modify the users of cpufreq_set_update_util_data() accordingly.

With the new helpers, the code using them doesn't need to worry
about the internals of struct update_util_data and in particular
it doesn't need to worry about populating the func field in it
properly upfront.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

New patch.

---
drivers/cpufreq/cpufreq_governor.c | 76 ++++++++++++++++++-------------------
drivers/cpufreq/intel_pstate.c | 8 +--
include/linux/sched.h | 5 +-
kernel/sched/cpufreq.c | 48 ++++++++++++++++++-----
4 files changed, 83 insertions(+), 54 deletions(-)

Index: linux-pm/include/linux/sched.h
===================================================================
--- linux-pm.orig/include/linux/sched.h
+++ linux-pm/include/linux/sched.h
@@ -3213,7 +3213,10 @@ struct update_util_data {
u64 time, unsigned long util, unsigned long max);
};

-void cpufreq_set_update_util_data(int cpu, struct update_util_data *data);
+void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
+ void (*func)(struct update_util_data *data, u64 time,
+ unsigned long util, unsigned long max));
+void cpufreq_remove_update_util_hook(int cpu);
#endif /* CONFIG_CPU_FREQ */

#endif
Index: linux-pm/kernel/sched/cpufreq.c
===================================================================
--- linux-pm.orig/kernel/sched/cpufreq.c
+++ linux-pm/kernel/sched/cpufreq.c
@@ -14,24 +14,50 @@
DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);

/**
- * cpufreq_set_update_util_data - Populate the CPU's update_util_data pointer.
+ * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
* @cpu: The CPU to set the pointer for.
* @data: New pointer value.
+ * @func: Callback function to set for the CPU.
*
- * Set and publish the update_util_data pointer for the given CPU. That pointer
- * points to a struct update_util_data object containing a callback function
- * to call from cpufreq_update_util(). That function will be called from an RCU
- * read-side critical section, so it must not sleep.
+ * Set and publish the update_util_data pointer for the given CPU.
*
- * Callers must use RCU-sched callbacks to free any memory that might be
- * accessed via the old update_util_data pointer or invoke synchronize_sched()
- * right after this function to avoid use-after-free.
+ * The update_util_data pointer of @cpu is set to @data and the callback
+ * function pointer in the target struct update_util_data is set to @func.
+ * That function will be called by cpufreq_update_util() from RCU-sched
+ * read-side critical sections, so it must not sleep. @data will always be
+ * passed to it as the first argument which allows the function to get to the
+ * target update_util_data structure and its container.
+ *
+ * The update_util_data pointer of @cpu must be NULL when this function is
+ * called or it will WARN() and return with no effect.
*/
-void cpufreq_set_update_util_data(int cpu, struct update_util_data *data)
+void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
+ void (*func)(struct update_util_data *data, u64 time,
+ unsigned long util, unsigned long max))
{
- if (WARN_ON(data && !data->func))
+ if (WARN_ON(!data || !func))
return;

+ if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
+ return;
+
+ data->func = func;
rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
}
-EXPORT_SYMBOL_GPL(cpufreq_set_update_util_data);
+EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
+
+/**
+ * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
+ * @cpu: The CPU to clear the pointer for.
+ *
+ * Clear the update_util_data pointer for the given CPU.
+ *
+ * Callers must use RCU-sched callbacks to free any memory that might be
+ * accessed via the old update_util_data pointer or invoke synchronize_sched()
+ * right after this function to avoid use-after-free.
+ */
+void cpufreq_remove_update_util_hook(int cpu)
+{
+ rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
+}
+EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
Index: linux-pm/drivers/cpufreq/cpufreq_governor.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c
+++ linux-pm/drivers/cpufreq/cpufreq_governor.c
@@ -258,43 +258,6 @@ unsigned int dbs_update(struct cpufreq_p
}
EXPORT_SYMBOL_GPL(dbs_update);

-static void gov_set_update_util(struct policy_dbs_info *policy_dbs,
- unsigned int delay_us)
-{
- struct cpufreq_policy *policy = policy_dbs->policy;
- int cpu;
-
- gov_update_sample_delay(policy_dbs, delay_us);
- policy_dbs->last_sample_time = 0;
-
- for_each_cpu(cpu, policy->cpus) {
- struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu);
-
- cpufreq_set_update_util_data(cpu, &cdbs->update_util);
- }
-}
-
-static inline void gov_clear_update_util(struct cpufreq_policy *policy)
-{
- int i;
-
- for_each_cpu(i, policy->cpus)
- cpufreq_set_update_util_data(i, NULL);
-
- synchronize_sched();
-}
-
-static void gov_cancel_work(struct cpufreq_policy *policy)
-{
- struct policy_dbs_info *policy_dbs = policy->governor_data;
-
- gov_clear_update_util(policy_dbs->policy);
- irq_work_sync(&policy_dbs->irq_work);
- cancel_work_sync(&policy_dbs->work);
- atomic_set(&policy_dbs->work_count, 0);
- policy_dbs->work_in_progress = false;
-}
-
static void dbs_work_handler(struct work_struct *work)
{
struct policy_dbs_info *policy_dbs;
@@ -382,6 +345,44 @@ static void dbs_update_util_handler(stru
irq_work_queue(&policy_dbs->irq_work);
}

+static void gov_set_update_util(struct policy_dbs_info *policy_dbs,
+ unsigned int delay_us)
+{
+ struct cpufreq_policy *policy = policy_dbs->policy;
+ int cpu;
+
+ gov_update_sample_delay(policy_dbs, delay_us);
+ policy_dbs->last_sample_time = 0;
+
+ for_each_cpu(cpu, policy->cpus) {
+ struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu);
+
+ cpufreq_add_update_util_hook(cpu, &cdbs->update_util,
+ dbs_update_util_handler);
+ }
+}
+
+static inline void gov_clear_update_util(struct cpufreq_policy *policy)
+{
+ int i;
+
+ for_each_cpu(i, policy->cpus)
+ cpufreq_remove_update_util_hook(i);
+
+ synchronize_sched();
+}
+
+static void gov_cancel_work(struct cpufreq_policy *policy)
+{
+ struct policy_dbs_info *policy_dbs = policy->governor_data;
+
+ gov_clear_update_util(policy_dbs->policy);
+ irq_work_sync(&policy_dbs->irq_work);
+ cancel_work_sync(&policy_dbs->work);
+ atomic_set(&policy_dbs->work_count, 0);
+ policy_dbs->work_in_progress = false;
+}
+
static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy,
struct dbs_governor *gov)
{
@@ -404,7 +405,6 @@ static struct policy_dbs_info *alloc_pol
struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j);

j_cdbs->policy_dbs = policy_dbs;
- j_cdbs->update_util.func = dbs_update_util_handler;
}
return policy_dbs;
}
Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -1089,8 +1089,8 @@ static int intel_pstate_init_cpu(unsigne
intel_pstate_busy_pid_reset(cpu);
intel_pstate_sample(cpu, 0);

- cpu->update_util.func = intel_pstate_update_util;
- cpufreq_set_update_util_data(cpunum, &cpu->update_util);
+ cpufreq_add_update_util_hook(cpunum, &cpu->update_util,
+ intel_pstate_update_util);

pr_debug("intel_pstate: controlling: cpu %d\n", cpunum);

@@ -1174,7 +1174,7 @@ static void intel_pstate_stop_cpu(struct

pr_debug("intel_pstate: CPU %d exiting\n", cpu_num);

- cpufreq_set_update_util_data(cpu_num, NULL);
+ cpufreq_remove_update_util_hook(cpu_num);
synchronize_sched();

if (hwp_active)
@@ -1442,7 +1442,7 @@ out:
get_online_cpus();
for_each_online_cpu(cpu) {
if (all_cpu_data[cpu]) {
- cpufreq_set_update_util_data(cpu, NULL);
+ cpufreq_remove_update_util_hook(cpu);
synchronize_sched();
kfree(all_cpu_data[cpu]);
}