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
  14 #ifndef _LINUX_EVENTPOLL_H
  15 #define _LINUX_EVENTPOLL_H
  16
  17 /* For O_CLOEXEC */
  18 #include <linux/fcntl.h>
  19 #include <linux/types.h>
  20
  21 /* Flags for epoll_create1.  */
  22 #define EPOLL_CLOEXEC O_CLOEXEC
  23
  24 /* Valid opcodes to issue to sys_epoll_ctl() */
  25 #define EPOLL_CTL_ADD 1
  26 #define EPOLL_CTL_DEL 2
  27 #define EPOLL_CTL_MOD 3
  28
  29 /* Set the One Shot behaviour for the target file descriptor */
  30 #define EPOLLONESHOT (1 << 30)
  31
  32 /* Set the Edge Triggered behaviour for the target file descriptor */
  33 #define EPOLLET (1 << 31)
  34
  35 /*
  36  * On x86-64 make the 64bit structure have the same alignment as the
  37  * 32bit structure. This makes 32bit emulation easier.
  38  *
  39  * UML/x86_64 needs the same packing as x86_64
  40  */
  41 #ifdef __x86_64__
  42 #define EPOLL_PACKED __attribute__((packed))
  43 #else
  44 #define EPOLL_PACKED
  45 #endif
  46
  47 struct epoll_event {
  48         __u32 events;
  49         __u64 data;
  50 } EPOLL_PACKED;
  51
  52 #ifdef __KERNEL__
  53
  54 /* Forward declarations to avoid compiler errors */
  55 struct file;
  56
  57
  58 #ifdef CONFIG_EPOLL
  59
  60 /* Used to initialize the epoll bits inside the "struct file" */
  61 static inline void eventpoll_init_file(struct file *file)
  62 {
  63         INIT_LIST_HEAD(&file->f_ep_links);
  64 }
  65
  66
  67 /* Used to release the epoll bits inside the "struct file" */
  68 void eventpoll_release_file(struct file *file);
  69
  70 /*
  71  * This is called from inside fs/file_table.c:__fput() to unlink files
  72  * from the eventpoll interface. We need to have this facility to cleanup
  73  * correctly files that are closed without being removed from the eventpoll
  74  * interface.
  75  */
  76 static inline void eventpoll_release(struct file *file)
  77 {
  78
  79         /*
  80          * Fast check to avoid the get/release of the semaphore. Since
  81          * we're doing this outside the semaphore lock, it might return
  82          * false negatives, but we don't care. It'll help in 99.99% of cases
  83          * to avoid the semaphore lock. False positives simply cannot happen
  84          * because the file in on the way to be removed and nobody ( but
  85          * eventpoll ) has still a reference to this file.
  86          */
  87         if (likely(list_empty(&file->f_ep_links)))
  88                 return;
  89
  90         /*
  91          * The file is being closed while it is still linked to an epoll
  92          * descriptor. We need to handle this by correctly unlinking it
  93          * from its containers.
  94          */
  95         eventpoll_release_file(file);
  96 }
  97
  98 #else
  99
 100 static inline void eventpoll_init_file(struct file *file) {}
 101 static inline void eventpoll_release(struct file *file) {}
 102
 103 #endif
 104
 105 #endif /* #ifdef __KERNEL__ */
 106
 107 #endif /* #ifndef _LINUX_EVENTPOLL_H */
 108