include/linux/eventpoll.h

   1 /*
   2  *  include/linux/eventpoll.h ( Efficent event polling implementation )
   3  *  Copyright (C) 2001,...,2003  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 #include <linux/types.h>
  18
  19
  20 /* Valid opcodes to issue to sys_epoll_ctl() */
  21 #define EPOLL_CTL_ADD 1
  22 #define EPOLL_CTL_DEL 2
  23 #define EPOLL_CTL_MOD 3
  24
  25 /* Set the One Shot behaviour for the target file descriptor */
  26 #define EPOLLONESHOT (1 << 30)
  27
  28 /* Set the Edge Triggered behaviour for the target file descriptor */
  29 #define EPOLLET (1 << 31)
  30
  31 /*
  32  * On x86-64 make the 64bit structure have the same alignment as the
  33  * 32bit structure. This makes 32bit emulation easier.
  34  */
  35 #ifdef __x86_64__
  36 #define EPOLL_PACKED __attribute__((packed))
  37 #else
  38 #define EPOLL_PACKED
  39 #endif
  40
  41 struct epoll_event {
  42         __u32 events;
  43         __u64 data;
  44 } EPOLL_PACKED;
  45
  46 #ifdef __KERNEL__
  47
  48 /* Forward declarations to avoid compiler errors */
  49 struct file;
  50
  51
  52 #ifdef CONFIG_EPOLL
  53
  54 /* Used to initialize the epoll bits inside the "struct file" */
  55 static inline void eventpoll_init_file(struct file *file)
  56 {
  57         INIT_LIST_HEAD(&file->f_ep_links);
  58         spin_lock_init(&file->f_ep_lock);
  59 }
  60
  61
  62 /* Used to release the epoll bits inside the "struct file" */
  63 void eventpoll_release_file(struct file *file);
  64
  65 /*
  66  * This is called from inside fs/file_table.c:__fput() to unlink files
  67  * from the eventpoll interface. We need to have this facility to cleanup
  68  * correctly files that are closed without being removed from the eventpoll
  69  * interface.
  70  */
  71 static inline void eventpoll_release(struct file *file)
  72 {
  73
  74         /*
  75          * Fast check to avoid the get/release of the semaphore. Since
  76          * we're doing this outside the semaphore lock, it might return
  77          * false negatives, but we don't care. It'll help in 99.99% of cases
  78          * to avoid the semaphore lock. False positives simply cannot happen
  79          * because the file in on the way to be removed and nobody ( but
  80          * eventpoll ) has still a reference to this file.
  81          */
  82         if (likely(list_empty(&file->f_ep_links)))
  83                 return;
  84
  85         /*
  86          * The file is being closed while it is still linked to an epoll
  87          * descriptor. We need to handle this by correctly unlinking it
  88          * from its containers.
  89          */
  90         eventpoll_release_file(file);
  91 }
  92
  93 #else
  94
  95 static inline void eventpoll_init_file(struct file *file) {}
  96 static inline void eventpoll_release(struct file *file) {}
  97
  98 #endif
  99
 100 #endif /* #ifdef __KERNEL__ */
 101
 102 #endif /* #ifndef _LINUX_EVENTPOLL_H */
 103