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 12 #include "sched.h" 13 14 DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data); 15 16 /** 17 * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer. 18 * @cpu: The CPU to set the pointer for. 19 * @data: New pointer value. 20 * @func: Callback function to set for the CPU. 21 * 22 * Set and publish the update_util_data pointer for the given CPU. 23 * 24 * The update_util_data pointer of @cpu is set to @data and the callback 25 * function pointer in the target struct update_util_data is set to @func. 26 * That function will be called by cpufreq_update_util() from RCU-sched 27 * read-side critical sections, so it must not sleep. @data will always be 28 * passed to it as the first argument which allows the function to get to the 29 * target update_util_data structure and its container. 30 * 31 * The update_util_data pointer of @cpu must be NULL when this function is 32 * called or it will WARN() and return with no effect. 33 */ 34 void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data, 35 void (*func)(struct update_util_data *data, u64 time, 36 unsigned int flags)) 37 { 38 if (WARN_ON(!data || !func)) 39 return; 40 41 if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu))) 42 return; 43 44 data->func = func; 45 rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data); 46 } 47 EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook); 48 49 /** 50 * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer. 51 * @cpu: The CPU to clear the pointer for. 52 * 53 * Clear the update_util_data pointer for the given CPU. 54 * 55 * Callers must use RCU-sched callbacks to free any memory that might be 56 * accessed via the old update_util_data pointer or invoke synchronize_sched() 57 * right after this function to avoid use-after-free. 58 */ 59 void cpufreq_remove_update_util_hook(int cpu) 60 { 61 rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL); 62 } 63 EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook); 64