Root/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
7static 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 */
14void 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, &__get_cpu_var(return_notifier_list));
18}
19EXPORT_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 */
25void user_return_notifier_unregister(struct user_return_notifier *urn)
26{
27    hlist_del(&urn->link);
28    if (hlist_empty(&__get_cpu_var(return_notifier_list)))
29        clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
30}
31EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
32
33/* Calls registered user return notifiers */
34void fire_user_return_notifiers(void)
35{
36    struct user_return_notifier *urn;
37    struct hlist_node *tmp1, *tmp2;
38    struct hlist_head *head;
39
40    head = &get_cpu_var(return_notifier_list);
41    hlist_for_each_entry_safe(urn, tmp1, tmp2, head, link)
42        urn->on_user_return(urn);
43    put_cpu_var(return_notifier_list);
44}
45

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