LXR linux/kernel/sched/cpufreq.c

   1/*
   2 * Scheduler code and data structures related to cpufreq.
   3 *
   4 * Copyright (C) 2016, Intel Corporation
   5 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 */
  11#include "sched.h"
  12
  13DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
  14
  15/**
  16 * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
  17 * @cpu: The CPU to set the pointer for.
  18 * @data: New pointer value.
  19 * @func: Callback function to set for the CPU.
  20 *
  21 * Set and publish the update_util_data pointer for the given CPU.
  22 *
  23 * The update_util_data pointer of @cpu is set to @data and the callback
  24 * function pointer in the target struct update_util_data is set to @func.
  25 * That function will be called by cpufreq_update_util() from RCU-sched
  26 * read-side critical sections, so it must not sleep.  @data will always be
  27 * passed to it as the first argument which allows the function to get to the
  28 * target update_util_data structure and its container.
  29 *
  30 * The update_util_data pointer of @cpu must be NULL when this function is
  31 * called or it will WARN() and return with no effect.
  32 */
  33void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
  34                        void (*func)(struct update_util_data *data, u64 time,
  35                                     unsigned int flags))
  36{
  37        if (WARN_ON(!data || !func))
  38                return;
  39
  40        if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
  41                return;
  42
  43        data->func = func;
  44        rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
  45}
  46EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
  47
  48/**
  49 * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
  50 * @cpu: The CPU to clear the pointer for.
  51 *
  52 * Clear the update_util_data pointer for the given CPU.
  53 *
  54 * Callers must use RCU callbacks to free any memory that might be
  55 * accessed via the old update_util_data pointer or invoke synchronize_rcu()
  56 * right after this function to avoid use-after-free.
  57 */
  58void cpufreq_remove_update_util_hook(int cpu)
  59{
  60        rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
  61}
  62EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
  63