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 */
  16 struct file;
  17
  18
  19 #ifdef CONFIG_EPOLL
  20
  21 #ifdef CONFIG_KCMP
  22 struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
  23 #endif
  24
  25 /* Used to release the epoll bits inside the "struct file" */
  26 void eventpoll_release_file(struct file *file);
  27
  28 /*
  29  * This is called from inside fs/file_table.c:__fput() to unlink files
  30  * from the eventpoll interface. We need to have this facility to cleanup
  31  * correctly files that are closed without being removed from the eventpoll
  32  * interface.
  33  */
  34 static inline void eventpoll_release(struct file *file)
  35 {
  36
  37         /*
  38          * Fast check to avoid the get/release of the semaphore. Since
  39          * we're doing this outside the semaphore lock, it might return
  40          * false negatives, but we don't care. It'll help in 99.99% of cases
  41          * to avoid the semaphore lock. False positives simply cannot happen
  42          * because the file in on the way to be removed and nobody ( but
  43          * eventpoll ) has still a reference to this file.
  44          */
  45         if (likely(!READ_ONCE(file->f_ep)))
  46                 return;
  47
  48         /*
  49          * The file is being closed while it is still linked to an epoll
  50          * descriptor. We need to handle this by correctly unlinking it
  51          * from its containers.
  52          */
  53         eventpoll_release_file(file);
  54 }
  55
  56 int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
  57                  bool nonblock);
  58
  59 /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
  60 static inline int ep_op_has_event(int op)
  61 {
  62         return op != EPOLL_CTL_DEL;
  63 }
  64
  65 #else
  66
  67 static inline void eventpoll_release(struct file *file) {}
  68
  69 #endif
  70
  71 #if defined(CONFIG_ARM) && defined(CONFIG_OABI_COMPAT)
  72 /* ARM OABI has an incompatible struct layout and needs a special handler */
  73 extern struct epoll_event __user *
  74 epoll_put_uevent(__poll_t revents, __u64 data,
  75                  struct epoll_event __user *uevent);
  76 #else
  77 static inline struct epoll_event __user *
  78 epoll_put_uevent(__poll_t revents, __u64 data,
  79                  struct epoll_event __user *uevent)
  80 {
  81         if (__put_user(revents, &uevent->events) ||
  82             __put_user(data, &uevent->data))
  83                 return NULL;
  84
  85         return uevent+1;
  86 }
  87 #endif
  88
  89 #endif /* #ifndef _LINUX_EVENTPOLL_H */