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       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                 :            : 
      18                 :            : 
      19                 :            : /* Forward declarations to avoid compiler errors */
      20                 :            : struct file;
      21                 :            : 
      22                 :            : 
      23                 :            : #ifdef CONFIG_EPOLL
      24                 :            : 
      25                 :            : /* Used to initialize the epoll bits inside the "struct file" */
      26                 :            : static inline void eventpoll_init_file(struct file *file)
      27                 :            : {
      28                 :    4514981 :         INIT_LIST_HEAD(&file->f_ep_links);
      29                 :    4514981 :         INIT_LIST_HEAD(&file->f_tfile_llink);
      30                 :            : }
      31                 :            : 
      32                 :            : 
      33                 :            : /* Used to release the epoll bits inside the "struct file" */
      34                 :            : void eventpoll_release_file(struct file *file);
      35                 :            : 
      36                 :            : /*
      37                 :            :  * This is called from inside fs/file_table.c:__fput() to unlink files
      38                 :            :  * from the eventpoll interface. We need to have this facility to cleanup
      39                 :            :  * correctly files that are closed without being removed from the eventpoll
      40                 :            :  * interface.
      41                 :            :  */
      42                 :            : static inline void eventpoll_release(struct file *file)
      43                 :            : {
      44                 :            : 
      45                 :            :         /*
      46                 :            :          * Fast check to avoid the get/release of the semaphore. Since
      47                 :            :          * we're doing this outside the semaphore lock, it might return
      48                 :            :          * false negatives, but we don't care. It'll help in 99.99% of cases
      49                 :            :          * to avoid the semaphore lock. False positives simply cannot happen
      50                 :            :          * because the file in on the way to be removed and nobody ( but
      51                 :            :          * eventpoll ) has still a reference to this file.
      52                 :            :          */
      53         [ -  + ]:    3874341 :         if (likely(list_empty(&file->f_ep_links)))
      54                 :            :                 return;
      55                 :            : 
      56                 :            :         /*
      57                 :            :          * The file is being closed while it is still linked to an epoll
      58                 :            :          * descriptor. We need to handle this by correctly unlinking it
      59                 :            :          * from its containers.
      60                 :            :          */
      61                 :          0 :         eventpoll_release_file(file);
      62                 :            : }
      63                 :            : 
      64                 :            : #else
      65                 :            : 
      66                 :            : static inline void eventpoll_init_file(struct file *file) {}
      67                 :            : static inline void eventpoll_release(struct file *file) {}
      68                 :            : 
      69                 :            : #endif
      70                 :            : 
      71                 :            : #endif /* #ifndef _LINUX_EVENTPOLL_H */