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 }
75
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