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 - UML + UML_X86 +
  36  * 64_BIT adds up to UML/x86_64.
  37  */
  38 #ifdef __x86_64__
  39 #define EPOLL_PACKED __attribute__((packed))
  40 #else
  41 #if defined(CONFIG_UML) && defined(CONFIG_UML_X86) && defined(CONFIG_64BIT)
  42 #define EPOLL_PACKED __attribute__((packed))
  43 #else
  44 #define EPOLL_PACKED
  45 #endif
  46 #endif
  47
  48 struct epoll_event {
  49         __u32 events;
  50         __u64 data;
  51 } EPOLL_PACKED;
  52
  53 #ifdef __KERNEL__
  54
  55 /* Forward declarations to avoid compiler errors */
  56 struct file;
  57
  58
  59 #ifdef CONFIG_EPOLL
  60
  61 /* Used to initialize the epoll bits inside the "struct file" */
  62 static inline void eventpoll_init_file(struct file *file)
  63 {
  64         INIT_LIST_HEAD(&file->f_ep_links);
  65         spin_lock_init(&file->f_ep_lock);
  66 }
  67
  68
  69 /* Used to release the epoll bits inside the "struct file" */
  70 void eventpoll_release_file(struct file *file);
  71
  72 /*
  73  * This is called from inside fs/file_table.c:__fput() to unlink files
  74  * from the eventpoll interface. We need to have this facility to cleanup
  75  * correctly files that are closed without being removed from the eventpoll
  76  * interface.
  77  */
  78 static inline void eventpoll_release(struct file *file)
  79 {
  80
  81         /*
  82          * Fast check to avoid the get/release of the semaphore. Since
  83          * we're doing this outside the semaphore lock, it might return
  84          * false negatives, but we don't care. It'll help in 99.99% of cases
  85          * to avoid the semaphore lock. False positives simply cannot happen
  86          * because the file in on the way to be removed and nobody ( but
  87          * eventpoll ) has still a reference to this file.
  88          */
  89         if (likely(list_empty(&file->f_ep_links)))
  90                 return;
  91
  92         /*
  93          * The file is being closed while it is still linked to an epoll
  94          * descriptor. We need to handle this by correctly unlinking it
  95          * from its containers.
  96          */
  97         eventpoll_release_file(file);
  98 }
  99
 100 #else
 101
 102 static inline void eventpoll_init_file(struct file *file) {}
 103 static inline void eventpoll_release(struct file *file) {}
 104
 105 #endif
 106
 107 #endif /* #ifdef __KERNEL__ */
 108
 109 #endif /* #ifndef _LINUX_EVENTPOLL_H */
 110