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