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1/*
2 * include/linux/eventpoll.h ( Efficent 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
14#ifndef _LINUX_EVENTPOLL_H
15#define _LINUX_EVENTPOLL_H
16
17#include <linux/types.h>
18
19
20/* Valid opcodes to issue to sys_epoll_ctl() */
21#define EPOLL_CTL_ADD 1
22#define EPOLL_CTL_DEL 2
23#define EPOLL_CTL_MOD 3
24
25/* Set the One Shot behaviour for the target file descriptor */
26#define EPOLLONESHOT (1 << 30)
27
28/* Set the Edge Triggered behaviour for the target file descriptor */
29#define EPOLLET (1 << 31)
30
31/*
32 * On x86-64 make the 64bit structure have the same alignment as the
33 * 32bit structure. This makes 32bit emulation easier.
34 *
35 * UML/x86_64 needs the same packing as x86_64
36 */
37#ifdef __x86_64__
38#define EPOLL_PACKED __attribute__((packed))
39#else
40#define EPOLL_PACKED
41#endif
42
43struct epoll_event {
44 __u32 events;
45 __u64 data;
46} EPOLL_PACKED;
47
48#ifdef __KERNEL__
49
50/* Forward declarations to avoid compiler errors */
51struct file;
52
53
54#ifdef CONFIG_EPOLL
55
56/* Used to initialize the epoll bits inside the "struct file" */
57static inline void eventpoll_init_file(struct file *file)
58{
59 INIT_LIST_HEAD(&file->f_ep_links);
60 spin_lock_init(&file->f_ep_lock);
61}
62
63
64/* Used to release the epoll bits inside the "struct file" */
65void eventpoll_release_file(struct file *file);
66
67/*
68 * This is called from inside fs/file_table.c:__fput() to unlink files
69 * from the eventpoll interface. We need to have this facility to cleanup
70 * correctly files that are closed without being removed from the eventpoll
71 * interface.
72 */
73static inline void eventpoll_release(struct file *file)
74{
75
76 /*
77 * Fast check to avoid the get/release of the semaphore. Since
78 * we're doing this outside the semaphore lock, it might return
79 * false negatives, but we don't care. It'll help in 99.99% of cases
80 * to avoid the semaphore lock. False positives simply cannot happen
81 * because the file in on the way to be removed and nobody ( but
82 * eventpoll ) has still a reference to this file.
83 */
84 if (likely(list_empty(&file->f_ep_links)))
85 return;
86
87 /*
88 * The file is being closed while it is still linked to an epoll
89 * descriptor. We need to handle this by correctly unlinking it
90 * from its containers.
91 */
92 eventpoll_release_file(file);
93}
94
95#else
96
97static inline void eventpoll_init_file(struct file *file) {}
98static inline void eventpoll_release(struct file *file) {}
99
100#endif
101
102#endif /* #ifdef __KERNEL__ */
103
104#endif /* #ifndef _LINUX_EVENTPOLL_H */
105