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#ifndef _LINUX_EVENTPOLL_H
  14#define _LINUX_EVENTPOLL_H
  15
  16#include <uapi/linux/eventpoll.h>
  17#include <uapi/linux/kcmp.h>
  18
  19
  20/* Forward declarations to avoid compiler errors */
  21struct file;
  22
  23
  24#ifdef CONFIG_EPOLL
  25
  26#ifdef CONFIG_CHECKPOINT_RESTORE
  27struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
  28#endif
  29
  30/* Used to initialize the epoll bits inside the "struct file" */
  31static inline void eventpoll_init_file(struct file *file)
  32{
  33        INIT_LIST_HEAD(&file->f_ep_links);
  34        INIT_LIST_HEAD(&file->f_tfile_llink);
  35}
  36
  37
  38/* Used to release the epoll bits inside the "struct file" */
  39void eventpoll_release_file(struct file *file);
  40
  41/*
  42 * This is called from inside fs/file_table.c:__fput() to unlink files
  43 * from the eventpoll interface. We need to have this facility to cleanup
  44 * correctly files that are closed without being removed from the eventpoll
  45 * interface.
  46 */
  47static inline void eventpoll_release(struct file *file)
  48{
  49
  50        /*
  51         * Fast check to avoid the get/release of the semaphore. Since
  52         * we're doing this outside the semaphore lock, it might return
  53         * false negatives, but we don't care. It'll help in 99.99% of cases
  54         * to avoid the semaphore lock. False positives simply cannot happen
  55         * because the file in on the way to be removed and nobody ( but
  56         * eventpoll ) has still a reference to this file.
  57         */
  58        if (likely(list_empty(&file->f_ep_links)))
  59                return;
  60
  61        /*
  62         * The file is being closed while it is still linked to an epoll
  63         * descriptor. We need to handle this by correctly unlinking it
  64         * from its containers.
  65         */
  66        eventpoll_release_file(file);
  67}
  68
  69#else
  70
  71static inline void eventpoll_init_file(struct file *file) {}
  72static inline void eventpoll_release(struct file *file) {}
  73
  74#endif
  75
  76#endif /* #ifndef _LINUX_EVENTPOLL_H */
  77