LXR linux/include/linux/eventpoll.h

   1/* SPDX-License-Identifier: GPL-2.0-or-later */
   2/*
   3 *  include/linux/eventpoll.h ( Efficient event polling implementation )
   4 *  Copyright (C) 2001,...,2006  Davide Libenzi
   5 *
   6 *  Davide Libenzi <davidel@xmailserver.org>
   7 */
   8#ifndef _LINUX_EVENTPOLL_H
   9#define _LINUX_EVENTPOLL_H
  10
  11#include <uapi/linux/eventpoll.h>
  12#include <uapi/linux/kcmp.h>
  13
  14
  15/* Forward declarations to avoid compiler errors */
  16struct file;
  17
  18
  19#ifdef CONFIG_EPOLL
  20
  21#ifdef CONFIG_CHECKPOINT_RESTORE
  22struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
  23#endif
  24
  25/* Used to initialize the epoll bits inside the "struct file" */
  26static inline void eventpoll_init_file(struct file *file)
  27{
  28        INIT_LIST_HEAD(&file->f_ep_links);
  29        INIT_LIST_HEAD(&file->f_tfile_llink);
  30}
  31
  32
  33/* Used to release the epoll bits inside the "struct file" */
  34void 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 */
  42static 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        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        eventpoll_release_file(file);
  62}
  63
  64int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
  65                 bool nonblock);
  66
  67/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
  68static inline int ep_op_has_event(int op)
  69{
  70        return op != EPOLL_CTL_DEL;
  71}
  72
  73#else
  74
  75static inline void eventpoll_init_file(struct file *file) {}
  76static inline void eventpoll_release(struct file *file) {}
  77
  78#endif
  79
  80#endif /* #ifndef _LINUX_EVENTPOLL_H */
  81