LXR linux/include/linux/eventpoll.h

   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/* Set the One Shot behaviour for the target file descriptor */
  30#define EPOLLONESHOT (1 << 30)
  31
  32/* Set the Edge Triggered behaviour for the target file descriptor */
  33#define EPOLLET (1 << 31)
  34
  35/* 
  36 * On x86-64 make the 64bit structure have the same alignment as the
  37 * 32bit structure. This makes 32bit emulation easier.
  38 *
  39 * UML/x86_64 needs the same packing as x86_64
  40 */
  41#ifdef __x86_64__
  42#define EPOLL_PACKED __attribute__((packed))
  43#else
  44#define EPOLL_PACKED
  45#endif
  46
  47struct epoll_event {
  48        __u32 events;
  49        __u64 data;
  50} EPOLL_PACKED;
  51
  52#ifdef __KERNEL__
  53
  54/* Forward declarations to avoid compiler errors */
  55struct file;
  56
  57
  58#ifdef CONFIG_EPOLL
  59
  60/* Used to initialize the epoll bits inside the "struct file" */
  61static inline void eventpoll_init_file(struct file *file)
  62{
  63        INIT_LIST_HEAD(&file->f_ep_links);
  64        INIT_LIST_HEAD(&file->f_tfile_llink);
  65}
  66
  67
  68/* Used to release the epoll bits inside the "struct file" */
  69void eventpoll_release_file(struct file *file);
  70
  71/*
  72 * This is called from inside fs/file_table.c:__fput() to unlink files
  73 * from the eventpoll interface. We need to have this facility to cleanup
  74 * correctly files that are closed without being removed from the eventpoll
  75 * interface.
  76 */
  77static inline void eventpoll_release(struct file *file)
  78{
  79
  80        /*
  81         * Fast check to avoid the get/release of the semaphore. Since
  82         * we're doing this outside the semaphore lock, it might return
  83         * false negatives, but we don't care. It'll help in 99.99% of cases
  84         * to avoid the semaphore lock. False positives simply cannot happen
  85         * because the file in on the way to be removed and nobody ( but
  86         * eventpoll ) has still a reference to this file.
  87         */
  88        if (likely(list_empty(&file->f_ep_links)))
  89                return;
  90
  91        /*
  92         * The file is being closed while it is still linked to an epoll
  93         * descriptor. We need to handle this by correctly unlinking it
  94         * from its containers.
  95         */
  96        eventpoll_release_file(file);
  97}
  98
  99#else
 100
 101static inline void eventpoll_init_file(struct file *file) {}
 102static inline void eventpoll_release(struct file *file) {}
 103
 104#endif
 105
 106#endif /* #ifdef __KERNEL__ */
 107
 108#endif /* #ifndef _LINUX_EVENTPOLL_H */
 109
 110