1 /* 2 * Scheduler code and data structures related to cpufreq. 3 * 4 * Copyright (C) 2016, Intel Corporation 5 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 #include "sched.h" 12 13 DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data); 14 15 /** 16 * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer. 17 * @cpu: The CPU to set the pointer for. 18 * @data: New pointer value. 19 * @func: Callback function to set for the CPU. 20 * 21 * Set and publish the update_util_data pointer for the given CPU. 22 * 23 * The update_util_data pointer of @cpu is set to @data and the callback 24 * function pointer in the target struct update_util_data is set to @func. 25 * That function will be called by cpufreq_update_util() from RCU-sched 26 * read-side critical sections, so it must not sleep. @data will always be 27 * passed to it as the first argument which allows the function to get to the 28 * target update_util_data structure and its container. 29 * 30 * The update_util_data pointer of @cpu must be NULL when this function is 31 * called or it will WARN() and return with no effect. 32 */ 33 void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data, 34 void (*func)(struct update_util_data *data, u64 time, 35 unsigned int flags)) 36 { 37 if (WARN_ON(!data || !func)) 38 return; 39 40 if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu))) 41 return; 42 43 data->func = func; 44 rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data); 45 } 46 EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook); 47 48 /** 49 * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer. 50 * @cpu: The CPU to clear the pointer for. 51 * 52 * Clear the update_util_data pointer for the given CPU. 53 * 54 * Callers must use RCU-sched callbacks to free any memory that might be 55 * accessed via the old update_util_data pointer or invoke synchronize_sched() 56 * right after this function to avoid use-after-free. 57 */ 58 void cpufreq_remove_update_util_hook(int cpu) 59 { 60 rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL); 61 } 62 EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook); 63