cpufreq.c 2.8 KB

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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. #include "sched.h"
  10. DEFINE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
  11. EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_update_util_data);
  12. /**
  13. * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
  14. * @cpu: The CPU to set the pointer for.
  15. * @data: New pointer value.
  16. * @func: Callback function to set for the CPU.
  17. *
  18. * Set and publish the update_util_data pointer for the given CPU.
  19. *
  20. * The update_util_data pointer of @cpu is set to @data and the callback
  21. * function pointer in the target struct update_util_data is set to @func.
  22. * That function will be called by cpufreq_update_util() from RCU-sched
  23. * read-side critical sections, so it must not sleep. @data will always be
  24. * passed to it as the first argument which allows the function to get to the
  25. * target update_util_data structure and its container.
  26. *
  27. * The update_util_data pointer of @cpu must be NULL when this function is
  28. * called or it will WARN() and return with no effect.
  29. */
  30. void cpufreq_add_update_util_hook(int cpu, struct update_util_data *data,
  31. void (*func)(struct update_util_data *data, u64 time,
  32. unsigned int flags))
  33. {
  34. if (WARN_ON(!data || !func))
  35. return;
  36. if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
  37. return;
  38. data->func = func;
  39. rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), data);
  40. }
  41. EXPORT_SYMBOL_GPL(cpufreq_add_update_util_hook);
  42. /**
  43. * cpufreq_remove_update_util_hook - Clear the CPU's update_util_data pointer.
  44. * @cpu: The CPU to clear the pointer for.
  45. *
  46. * Clear the update_util_data pointer for the given CPU.
  47. *
  48. * Callers must use RCU callbacks to free any memory that might be
  49. * accessed via the old update_util_data pointer or invoke synchronize_rcu()
  50. * right after this function to avoid use-after-free.
  51. */
  52. void cpufreq_remove_update_util_hook(int cpu)
  53. {
  54. rcu_assign_pointer(per_cpu(cpufreq_update_util_data, cpu), NULL);
  55. }
  56. EXPORT_SYMBOL_GPL(cpufreq_remove_update_util_hook);
  57. /**
  58. * cpufreq_this_cpu_can_update - Check if cpufreq policy can be updated.
  59. * @policy: cpufreq policy to check.
  60. *
  61. * Return 'true' if:
  62. * - the local and remote CPUs share @policy,
  63. * - dvfs_possible_from_any_cpu is set in @policy and the local CPU is not going
  64. * offline (in which case it is not expected to run cpufreq updates any more).
  65. */
  66. bool cpufreq_this_cpu_can_update(struct cpufreq_policy *policy)
  67. {
  68. return cpumask_test_cpu(smp_processor_id(), policy->cpus) ||
  69. (policy->dvfs_possible_from_any_cpu &&
  70. rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)));
  71. }
  72. EXPORT_SYMBOL_GPL(cpufreq_this_cpu_can_update);