user-return-notifier.c 1.3 KB

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  1. // SPDX-License-Identifier: GPL-2.0-only
  2. #include <linux/user-return-notifier.h>
  3. #include <linux/percpu.h>
  4. #include <linux/sched.h>
  5. #include <linux/export.h>
  6. static DEFINE_PER_CPU(struct hlist_head, return_notifier_list);
  7. /*
  8. * Request a notification when the current cpu returns to userspace. Must be
  9. * called in atomic context. The notifier will also be called in atomic
  10. * context.
  11. */
  12. void user_return_notifier_register(struct user_return_notifier *urn)
  13. {
  14. set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
  15. hlist_add_head(&urn->link, this_cpu_ptr(&return_notifier_list));
  16. }
  17. EXPORT_SYMBOL_GPL(user_return_notifier_register);
  18. /*
  19. * Removes a registered user return notifier. Must be called from atomic
  20. * context, and from the same cpu registration occurred in.
  21. */
  22. void user_return_notifier_unregister(struct user_return_notifier *urn)
  23. {
  24. hlist_del(&urn->link);
  25. if (hlist_empty(this_cpu_ptr(&return_notifier_list)))
  26. clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
  27. }
  28. EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
  29. /* Calls registered user return notifiers */
  30. void fire_user_return_notifiers(void)
  31. {
  32. struct user_return_notifier *urn;
  33. struct hlist_node *tmp2;
  34. struct hlist_head *head;
  35. head = &get_cpu_var(return_notifier_list);
  36. hlist_for_each_entry_safe(urn, tmp2, head, link)
  37. urn->on_user_return(urn);
  38. put_cpu_var(return_notifier_list);
  39. }