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
  12 #include "sched.h"
  13
  14 DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
  15
  16 /**
  17  * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
  18  * @cpu: The CPU to set the pointer for.
  19  * @data: New pointer value.
  20  * @func: Callback function to set for the CPU.
  21  *
  22  * Set and publish the update_util_data pointer for the given CPU.
  23  *
  24  * The update_util_data pointer of @cpu is set to @data and the callback
  25  * function pointer in the target struct update_util_data is set to @func.
  26  * That function will be called by cpufreq_update_util() from RCU-sched
  27  * read-side critical sections, so it must not sleep.  @data will always be
  28  * passed to it as the first argument which allows the function to get to the
  29  * target update_util_data structure and its container.
  30  *
  31  * The update_util_data pointer of @cpu must be NULL when this function is
  32  * called or it will WARN() and return with no effect.
  33  */
  34 void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
  35                         void (*func)(struct update_util_data *data, u64 time,
  36                                      unsigned int flags))
  37 {
  38         if (WARN_ON(!data || !func))
  39                 return;
  40
  41         if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
  42                 return;
  43
  44         data->func = func;
  45         rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
  46 }
  47 EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
  48
  49 /**
  50  * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
  51  * @cpu: The CPU to clear the pointer for.
  52  *
  53  * Clear the update_util_data pointer for the given CPU.
  54  *
  55  * Callers must use RCU-sched callbacks to free any memory that might be
  56  * accessed via the old update_util_data pointer or invoke synchronize_sched()
  57  * right after this function to avoid use-after-free.
  58  */
  59 void cpufreq_remove_update_util_hook(int cpu)
  60 {
  61         rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
  62 }
  63 EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);