kernel/sched/cpufreq.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Scheduler code and data structures related to cpufreq.
0004  *
0005  * Copyright (C) 2016, Intel Corporation
0006  * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
0007  */
0008
0009 DEFINE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
0010
0011 /**
0012  * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
0013  * @cpu: The CPU to set the pointer for.
0014  * @data: New pointer value.
0015  * @func: Callback function to set for the CPU.
0016  *
0017  * Set and publish the update_util_data pointer for the given CPU.
0018  *
0019  * The update_util_data pointer of @cpu is set to @data and the callback
0020  * function pointer in the target struct update_util_data is set to @func.
0021  * That function will be called by cpufreq_update_util() from RCU-sched
0022  * read-side critical sections, so it must not sleep.  @data will always be
0023  * passed to it as the first argument which allows the function to get to the
0024  * target update_util_data structure and its container.
0025  *
0026  * The update_util_data pointer of @cpu must be NULL when this function is
0027  * called or it will WARN() and return with no effect.
0028  */
0029 void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
0030             void (*func)(struct update_util_data *data, u64 time,
0031                      unsigned int flags))
0032 {
0033     if (WARN_ON(!data || !func))
0034         return;
0035
0036     if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
0037         return;
0038
0039     data->func = func;
0040     rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
0041 }
0042 EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
0043
0044 /**
0045  * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
0046  * @cpu: The CPU to clear the pointer for.
0047  *
0048  * Clear the update_util_data pointer for the given CPU.
0049  *
0050  * Callers must use RCU callbacks to free any memory that might be
0051  * accessed via the old update_util_data pointer or invoke synchronize_rcu()
0052  * right after this function to avoid use-after-free.
0053  */
0054 void cpufreq_remove_update_util_hook(int cpu)
0055 {
0056     rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
0057 }
0058 EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
0059
0060 /**
0061  * cpufreq_this_cpu_can_update - Check if cpufreq policy can be updated.
0062  * @policy: cpufreq policy to check.
0063  *
0064  * Return 'true' if:
0065  * - the local and remote CPUs share @policy,
0066  * - dvfs_possible_from_any_cpu is set in @policy and the local CPU is not going
0067  *   offline (in which case it is not expected to run cpufreq updates any more).
0068  */
0069 bool cpufreq_this_cpu_can_update(struct cpufreq_policy *policy)
0070 {
0071     return cpumask_test_cpu(smp_processor_id(), policy->cpus) ||
0072         (policy->dvfs_possible_from_any_cpu &&
0073          rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)));
0074 }