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
  10 DEFINE_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  */
  30 void 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 }
  43 EXPORT_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  */
  55 void cpufreq_remove_update_util_hook(int cpu)
  56 {
  57         rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
  58 }
  59 EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);