cregit-Linux how code gets into the kernel

Release 4.15 kernel/sched/cpufreq.c

Directory: kernel/sched
 * Scheduler code and data structures related to cpufreq.
 * Copyright (C) 2016, Intel Corporation
 * Author: Rafael J. Wysocki <>
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.

#include "sched.h"

DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);

 * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
 * @cpu: The CPU to set the pointer for.
 * @data: New pointer value.
 * @func: Callback function to set for the CPU.
 * Set and publish the update_util_data pointer for the given CPU.
 * The update_util_data pointer of @cpu is set to @data and the callback
 * function pointer in the target struct update_util_data is set to @func.
 * That function will be called by cpufreq_update_util() from RCU-sched
 * read-side critical sections, so it must not sleep.  @data will always be
 * passed to it as the first argument which allows the function to get to the
 * target update_util_data structure and its container.
 * The update_util_data pointer of @cpu must be NULL when this function is
 * called or it will WARN() and return with no effect.

void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data, void (*func)(struct update_util_data *data, u64 time, unsigned int flags)) { if (WARN_ON(!data || !func)) return; if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu))) return; data->func = func; rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data); }


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EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook); /** * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer. * @cpu: The CPU to clear the pointer for. * * Clear the update_util_data pointer for the given CPU. * * Callers must use RCU-sched callbacks to free any memory that might be * accessed via the old update_util_data pointer or invoke synchronize_sched() * right after this function to avoid use-after-free. */
void cpufreq_remove_update_util_hook(int cpu) { rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL); }


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Rafael J. Wysocki120100.00%3100.00%
Directory: kernel/sched
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