/*
   * 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 int flags))
  {
  	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);