1/*
2 *  include/linux/eventpoll.h ( Efficient event polling implementation )
3 *  Copyright (C) 2001,...,2006	 Davide Libenzi
4 *
5 *  This program is free software; you can redistribute it and/or modify
6 *  it under the terms of the GNU General Public License as published by
7 *  the Free Software Foundation; either version 2 of the License, or
8 *  (at your option) any later version.
9 *
10 *  Davide Libenzi <davidel@xmailserver.org>
11 *
12 */
13#ifndef _LINUX_EVENTPOLL_H
14#define _LINUX_EVENTPOLL_H
15
16#include <uapi/linux/eventpoll.h>
17
18
19/* Forward declarations to avoid compiler errors */
20struct file;
21
22
23#ifdef CONFIG_EPOLL
24
25/* Used to initialize the epoll bits inside the "struct file" */
26static inline void eventpoll_init_file(struct file *file)
27{
28	INIT_LIST_HEAD(&file->f_ep_links);
29	INIT_LIST_HEAD(&file->f_tfile_llink);
30}
31
32
33/* Used to release the epoll bits inside the "struct file" */
34void eventpoll_release_file(struct file *file);
35
36/*
37 * This is called from inside fs/file_table.c:__fput() to unlink files
38 * from the eventpoll interface. We need to have this facility to cleanup
39 * correctly files that are closed without being removed from the eventpoll
40 * interface.
41 */
42static inline void eventpoll_release(struct file *file)
43{
44
45	/*
46	 * Fast check to avoid the get/release of the semaphore. Since
47	 * we're doing this outside the semaphore lock, it might return
48	 * false negatives, but we don't care. It'll help in 99.99% of cases
49	 * to avoid the semaphore lock. False positives simply cannot happen
50	 * because the file in on the way to be removed and nobody ( but
51	 * eventpoll ) has still a reference to this file.
52	 */
53	if (likely(list_empty(&file->f_ep_links)))
54		return;
55
56	/*
57	 * The file is being closed while it is still linked to an epoll
58	 * descriptor. We need to handle this by correctly unlinking it
59	 * from its containers.
60	 */
61	eventpoll_release_file(file);
62}
63
64#else
65
66static inline void eventpoll_init_file(struct file *file) {}
67static inline void eventpoll_release(struct file *file) {}
68
69#endif
70
71#endif /* #ifndef _LINUX_EVENTPOLL_H */
72