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 }