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 */
  21 struct file;
  22
  23
  24 #ifdef CONFIG_EPOLL
  25
  26 #ifdef CONFIG_CHECKPOINT_RESTORE
  27 struct 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" */
  31 static 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" */
  39 void 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  */
  47 static 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
  71 static inline void eventpoll_init_file(struct file *file) {}
  72 static inline void eventpoll_release(struct file *file) {}
  73
  74 #endif
  75
  76 #endif /* #ifndef _LINUX_EVENTPOLL_H */