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 <linux/cpufreq.h>
   9
  10#include "sched.h"
  11
  12DEFINE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
  13
  14/**
  15 * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
  16 * @cpu: The CPU to set the pointer for.
  17 * @data: New pointer value.
  18 * @func: Callback function to set for the CPU.
  19 *
  20 * Set and publish the update_util_data pointer for the given CPU.
  21 *
  22 * The update_util_data pointer of @cpu is set to @data and the callback
  23 * function pointer in the target struct update_util_data is set to @func.
  24 * That function will be called by cpufreq_update_util() from RCU-sched
  25 * read-side critical sections, so it must not sleep.  @data will always be
  26 * passed to it as the first argument which allows the function to get to the
  27 * target update_util_data structure and its container.
  28 *
  29 * The update_util_data pointer of @cpu must be NULL when this function is
  30 * called or it will WARN() and return with no effect.
  31 */
  32void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
  33                        void (*func)(struct update_util_data *data, u64 time,
  34                                     unsigned int flags))
  35{
  36        if (WARN_ON(!data || !func))
  37                return;
  38
  39        if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
  40                return;
  41
  42        data->func = func;
  43        rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
  44}
  45EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
  46
  47/**
  48 * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
  49 * @cpu: The CPU to clear the pointer for.
  50 *
  51 * Clear the update_util_data pointer for the given CPU.
  52 *
  53 * Callers must use RCU callbacks to free any memory that might be
  54 * accessed via the old update_util_data pointer or invoke synchronize_rcu()
  55 * right after this function to avoid use-after-free.
  56 */
  57void cpufreq_remove_update_util_hook(int cpu)
  58{
  59        rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
  60}
  61EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
  62
  63/**
  64 * cpufreq_this_cpu_can_update - Check if cpufreq policy can be updated.
  65 * @policy: cpufreq policy to check.
  66 *
  67 * Return 'true' if:
  68 * - the local and remote CPUs share @policy,
  69 * - dvfs_possible_from_any_cpu is set in @policy and the local CPU is not going
  70 *   offline (in which case it is not expected to run cpufreq updates any more).
  71 */
  72bool cpufreq_this_cpu_can_update(struct cpufreq_policy *policy)
  73{
  74        return cpumask_test_cpu(smp_processor_id(), policy->cpus) ||
  75                (policy->dvfs_possible_from_any_cpu &&
  76                 rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)));
  77}
  78