1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * include/linux/eventpoll.h ( Efficient event polling implementation )
4 * Copyright (C) 2001,...,2006 Davide Libenzi
5 *
6 * Davide Libenzi <davidel@xmailserver.org>
7 */
8 #ifndef _LINUX_EVENTPOLL_H
9 #define _LINUX_EVENTPOLL_H
10
11 #include <uapi/linux/eventpoll.h>
12 #include <uapi/linux/kcmp.h>
13
14
15 /* Forward declarations to avoid compiler errors */
16 struct file;
17
18
19 #ifdef CONFIG_EPOLL
20
21 #ifdef CONFIG_CHECKPOINT_RESTORE
22 struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
23 #endif
24
25 /* Used to initialize the epoll bits inside the "struct file" */
26 static 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" */
34 void 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 */
42 static 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
66 static inline void eventpoll_init_file(struct file *file) {}
67 static inline void eventpoll_release(struct file *file) {}
68
69 #endif
70
71 #endif /* #ifndef _LINUX_EVENTPOLL_H */