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Linux/kernel/sched/cpufreq.c

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  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 }
 78 

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