path: root/kernel/user-return-notifier.c (plain)
blob: 9586b670a5b27fef9d4e4f49d8e515059f02d6e4

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	}
45