linux/include/linux/eventpoll.h
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   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
  14#ifndef _LINUX_EVENTPOLL_H
  15#define _LINUX_EVENTPOLL_H
  16
  17/* For O_CLOEXEC */
  18#include <linux/fcntl.h>
  19#include <linux/types.h>
  20
  21/* Flags for epoll_create1.  */
  22#define EPOLL_CLOEXEC O_CLOEXEC
  23
  24/* Valid opcodes to issue to sys_epoll_ctl() */
  25#define EPOLL_CTL_ADD 1
  26#define EPOLL_CTL_DEL 2
  27#define EPOLL_CTL_MOD 3
  28
  29/*
  30 * Request the handling of system wakeup events so as to prevent system suspends
  31 * from happening while those events are being processed.
  32 *
  33 * Assuming neither EPOLLET nor EPOLLONESHOT is set, system suspends will not be
  34 * re-allowed until epoll_wait is called again after consuming the wakeup
  35 * event(s).
  36 *
  37 * Requires CAP_BLOCK_SUSPEND
  38 */
  39#define EPOLLWAKEUP (1 << 29)
  40
  41/* Set the One Shot behaviour for the target file descriptor */
  42#define EPOLLONESHOT (1 << 30)
  43
  44/* Set the Edge Triggered behaviour for the target file descriptor */
  45#define EPOLLET (1 << 31)
  46
  47/* 
  48 * On x86-64 make the 64bit structure have the same alignment as the
  49 * 32bit structure. This makes 32bit emulation easier.
  50 *
  51 * UML/x86_64 needs the same packing as x86_64
  52 */
  53#ifdef __x86_64__
  54#define EPOLL_PACKED __attribute__((packed))
  55#else
  56#define EPOLL_PACKED
  57#endif
  58
  59struct epoll_event {
  60        __u32 events;
  61        __u64 data;
  62} EPOLL_PACKED;
  63
  64#ifdef __KERNEL__
  65
  66/* Forward declarations to avoid compiler errors */
  67struct file;
  68
  69
  70#ifdef CONFIG_EPOLL
  71
  72/* Used to initialize the epoll bits inside the "struct file" */
  73static inline void eventpoll_init_file(struct file *file)
  74{
  75        INIT_LIST_HEAD(&file->f_ep_links);
  76        INIT_LIST_HEAD(&file->f_tfile_llink);
  77}
  78
  79
  80/* Used to release the epoll bits inside the "struct file" */
  81void eventpoll_release_file(struct file *file);
  82
  83/*
  84 * This is called from inside fs/file_table.c:__fput() to unlink files
  85 * from the eventpoll interface. We need to have this facility to cleanup
  86 * correctly files that are closed without being removed from the eventpoll
  87 * interface.
  88 */
  89static inline void eventpoll_release(struct file *file)
  90{
  91
  92        /*
  93         * Fast check to avoid the get/release of the semaphore. Since
  94         * we're doing this outside the semaphore lock, it might return
  95         * false negatives, but we don't care. It'll help in 99.99% of cases
  96         * to avoid the semaphore lock. False positives simply cannot happen
  97         * because the file in on the way to be removed and nobody ( but
  98         * eventpoll ) has still a reference to this file.
  99         */
 100        if (likely(list_empty(&file->f_ep_links)))
 101                return;
 102
 103        /*
 104         * The file is being closed while it is still linked to an epoll
 105         * descriptor. We need to handle this by correctly unlinking it
 106         * from its containers.
 107         */
 108        eventpoll_release_file(file);
 109}
 110
 111#else
 112
 113static inline void eventpoll_init_file(struct file *file) {}
 114static inline void eventpoll_release(struct file *file) {}
 115
 116#endif
 117
 118#endif /* #ifdef __KERNEL__ */
 119
 120#endif /* #ifndef _LINUX_EVENTPOLL_H */
 121
 122
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