LXR linux/kernel/user-return-notifier.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2
   3#include <linux/user-return-notifier.h>
   4#include <linux/percpu.h>
   5#include <linux/sched.h>
   6#include <linux/export.h>
   7
   8static DEFINE_PER_CPU(struct hlist_head, return_notifier_list);
   9
  10/*
  11 * Request a notification when the current cpu returns to userspace.  Must be
  12 * called in atomic context.  The notifier will also be called in atomic
  13 * context.
  14 */
  15void user_return_notifier_register(struct user_return_notifier *urn)
  16{
  17        set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
  18        hlist_add_head(&urn->link, this_cpu_ptr(&return_notifier_list));
  19}
  20EXPORT_SYMBOL_GPL(user_return_notifier_register);
  21
  22/*
  23 * Removes a registered user return notifier.  Must be called from atomic
  24 * context, and from the same cpu registration occurred in.
  25 */
  26void user_return_notifier_unregister(struct user_return_notifier *urn)
  27{
  28        hlist_del(&urn->link);
  29        if (hlist_empty(this_cpu_ptr(&return_notifier_list)))
  30                clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
  31}
  32EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
  33
  34/* Calls registered user return notifiers */
  35void fire_user_return_notifiers(void)
  36{
  37        struct user_return_notifier *urn;
  38        struct hlist_node *tmp2;
  39        struct hlist_head *head;
  40
  41        head = &get_cpu_var(return_notifier_list);
  42        hlist_for_each_entry_safe(urn, tmp2, head, link)
  43                urn->on_user_return(urn);
  44        put_cpu_var(return_notifier_list);
  45}
  46