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       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                 :          2 : 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                 :          2 :         if (WARN_ON(!data || !func))
      37                 :            :                 return;
      38                 :            : 
      39                 :          2 :         if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
      40                 :            :                 return;
      41                 :            : 
      42                 :          2 :         data->func = func;
      43                 :          2 :         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                 :          0 : void cpufreq_remove_update_util_hook(int cpu)
      58                 :            : {
      59                 :          0 :         rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
      60                 :          0 : }
      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                 :          2 : bool cpufreq_this_cpu_can_update(struct cpufreq_policy *policy)
      73                 :            : {
      74                 :          2 :         return cpumask_test_cpu(smp_processor_id(), policy->cpus) ||
      75                 :          0 :                 (policy->dvfs_possible_from_any_cpu &&
      76                 :          0 :                  rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)));
      77                 :            : }