LXR linux/kernel/sched/cpufreq.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Scheduler code and data structures related to cpufreq.
   4 *
   5 * Copyright (C) 2016, Intel Corporation
   6 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
   7 */
   8#include "sched.h"
   9
  10DEFINE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
  11
  12/**
  13 * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
  14 * @cpu: The CPU to set the pointer for.
  15 * @data: New pointer value.
  16 * @func: Callback function to set for the CPU.
  17 *
  18 * Set and publish the update_util_data pointer for the given CPU.
  19 *
  20 * The update_util_data pointer of @cpu is set to @data and the callback
  21 * function pointer in the target struct update_util_data is set to @func.
  22 * That function will be called by cpufreq_update_util() from RCU-sched
  23 * read-side critical sections, so it must not sleep.  @data will always be
  24 * passed to it as the first argument which allows the function to get to the
  25 * target update_util_data structure and its container.
  26 *
  27 * The update_util_data pointer of @cpu must be NULL when this function is
  28 * called or it will WARN() and return with no effect.
  29 */
  30void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
  31                        void (*func)(struct update_util_data *data, u64 time,
  32                                     unsigned int flags))
  33{
  34        if (WARN_ON(!data || !func))
  35                return;
  36
  37        if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
  38                return;
  39
  40        data->func = func;
  41        rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
  42}
  43EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
  44
  45/**
  46 * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
  47 * @cpu: The CPU to clear the pointer for.
  48 *
  49 * Clear the update_util_data pointer for the given CPU.
  50 *
  51 * Callers must use RCU callbacks to free any memory that might be
  52 * accessed via the old update_util_data pointer or invoke synchronize_rcu()
  53 * right after this function to avoid use-after-free.
  54 */
  55void cpufreq_remove_update_util_hook(int cpu)
  56{
  57        rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
  58}
  59EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
  60