linux/kernel/sched/cpufreq.c
Rafael J. Wysocki 0bed612be6 cpufreq: sched: Helpers to add and remove update_util hooks
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>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2016-04-02 01:08:43 +02:00

64 lines
2.2 KiB
C

/*
* Scheduler code and data structures related to cpufreq.
*
* Copyright (C) 2016, Intel Corporation
* Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include "sched.h"
DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
/**
* 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.
*
* 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_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 || !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_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);