1 | // SPDX-License-Identifier: GPL-2.0-only |
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2 | |
3 | #include <linux/user-return-notifier.h> |
4 | #include <linux/percpu.h> |
5 | #include <linux/sched.h> |
6 | #include <linux/export.h> |
7 | |
8 | static 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 | */ |
15 | void user_return_notifier_register(struct user_return_notifier *urn) |
16 | { |
17 | set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY); |
18 | hlist_add_head(n: &urn->link, this_cpu_ptr(&return_notifier_list)); |
19 | } |
20 | EXPORT_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 | */ |
26 | void user_return_notifier_unregister(struct user_return_notifier *urn) |
27 | { |
28 | hlist_del(n: &urn->link); |
29 | if (hlist_empty(this_cpu_ptr(&return_notifier_list))) |
30 | clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY); |
31 | } |
32 | EXPORT_SYMBOL_GPL(user_return_notifier_unregister); |
33 | |
34 | /* Calls registered user return notifiers */ |
35 | void 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 |