kernel/user-return-notifier.c

   1
   2 #include <linux/user-return-notifier.h>
   3 #include <linux/percpu.h>
   4 #include <linux/sched.h>
   5 #include <linux/export.h>
   6
   7 static DEFINE_PER_CPU(struct hlist_head, return_notifier_list);
   8
   9 /*
  10  * Request a notification when the current cpu returns to userspace.  Must be
  11  * called in atomic context.  The notifier will also be called in atomic
  12  * context.
  13  */
  14 void user_return_notifier_register(struct user_return_notifier *urn)
  15 {
  16         set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
  17         hlist_add_head(&urn->link, this_cpu_ptr(&return_notifier_list));
  18 }
  19 EXPORT_SYMBOL_GPL(user_return_notifier_register);
  20
  21 /*
  22  * Removes a registered user return notifier.  Must be called from atomic
  23  * context, and from the same cpu registration occurred in.
  24  */
  25 void user_return_notifier_unregister(struct user_return_notifier *urn)
  26 {
  27         hlist_del(&urn->link);
  28         if (hlist_empty(this_cpu_ptr(&return_notifier_list)))
  29                 clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
  30 }
  31 EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
  32
  33 /* Calls registered user return notifiers */
  34 void fire_user_return_notifiers(void)
  35 {
  36         struct user_return_notifier *urn;
  37         struct hlist_node *tmp2;
  38         struct hlist_head *head;
  39
  40         head = &get_cpu_var(return_notifier_list);
  41         hlist_for_each_entry_safe(urn, tmp2, head, link)
  42                 urn->on_user_return(urn);
  43         put_cpu_var(return_notifier_list);
  44 }