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