include/linux/eventpoll.h

   1 /*
   2  *  include/linux/eventpoll.h ( Efficent 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
  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  * UML/x86_64 needs the same packing as x86_64
  36  */
  37 #ifdef __x86_64__
  38 #define EPOLL_PACKED __attribute__((packed))
  39 #else
  40 #define EPOLL_PACKED
  41 #endif
  42
  43 struct epoll_event {
  44         __u32 events;
  45         __u64 data;
  46 } EPOLL_PACKED;
  47
  48 #ifdef __KERNEL__
  49
  50 /* Forward declarations to avoid compiler errors */
  51 struct file;
  52
  53
  54 #ifdef CONFIG_EPOLL
  55
  56 /* Used to initialize the epoll bits inside the "struct file" */
  57 static inline void eventpoll_init_file(struct file *file)
  58 {
  59         INIT_LIST_HEAD(&file->f_ep_links);
  60         spin_lock_init(&file->f_ep_lock);
  61 }
  62
  63
  64 /* Used to release the epoll bits inside the "struct file" */
  65 void eventpoll_release_file(struct file *file);
  66
  67 /*
  68  * This is called from inside fs/file_table.c:__fput() to unlink files
  69  * from the eventpoll interface. We need to have this facility to cleanup
  70  * correctly files that are closed without being removed from the eventpoll
  71  * interface.
  72  */
  73 static inline void eventpoll_release(struct file *file)
  74 {
  75
  76         /*
  77          * Fast check to avoid the get/release of the semaphore. Since
  78          * we're doing this outside the semaphore lock, it might return
  79          * false negatives, but we don't care. It'll help in 99.99% of cases
  80          * to avoid the semaphore lock. False positives simply cannot happen
  81          * because the file in on the way to be removed and nobody ( but
  82          * eventpoll ) has still a reference to this file.
  83          */
  84         if (likely(list_empty(&file->f_ep_links)))
  85                 return;
  86
  87         /*
  88          * The file is being closed while it is still linked to an epoll
  89          * descriptor. We need to handle this by correctly unlinking it
  90          * from its containers.
  91          */
  92         eventpoll_release_file(file);
  93 }
  94
  95 #else
  96
  97 static inline void eventpoll_init_file(struct file *file) {}
  98 static inline void eventpoll_release(struct file *file) {}
  99
 100 #endif
 101
 102 #endif /* #ifdef __KERNEL__ */
 103
 104 #endif /* #ifndef _LINUX_EVENTPOLL_H */
 105