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
  18
  19/* Forward declarations to avoid compiler errors */
  20struct file;
  21
  22
  23#ifdef CONFIG_EPOLL
  24
  25/* Used to initialize the epoll bits inside the "struct file" */
  26static 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" */
  34void 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 */
  42static 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
  66static inline void eventpoll_init_file(struct file *file) {}
  67static inline void eventpoll_release(struct file *file) {}
  68
  69#endif
  70
  71#endif /* #ifndef _LINUX_EVENTPOLL_H */
  72