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
  12 DEFINE_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  */
  32 void 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 }
  45 EXPORT_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  */
  57 void cpufreq_remove_update_util_hook(int cpu)
  58 {
  59         rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
  60 }
  61 EXPORT_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  */
  72 bool 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 }