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