[mirror_ubuntu-eoan-kernel.git] / include / linux / eventpoll.h

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 *  include/linux/eventpoll.h ( Efficient event polling implementation )
 *  Copyright (C) 2001,...,2006	 Davide Libenzi
 *
 *  Davide Libenzi <davidel@xmailserver.org>
 */
#ifndef _LINUX_EVENTPOLL_H
#define _LINUX_EVENTPOLL_H

#include <uapi/linux/eventpoll.h>
#include <uapi/linux/kcmp.h>


/* Forward declarations to avoid compiler errors */
struct file;


#ifdef CONFIG_EPOLL

#ifdef CONFIG_CHECKPOINT_RESTORE
struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
#endif

/* Used to initialize the epoll bits inside the "struct file" */
static inline void eventpoll_init_file(struct file *file)
{
	INIT_LIST_HEAD(&file->f_ep_links);
	INIT_LIST_HEAD(&file->f_tfile_llink);
}


/* Used to release the epoll bits inside the "struct file" */
void eventpoll_release_file(struct file *file);

/*
 * This is called from inside fs/file_table.c:__fput() to unlink files
 * from the eventpoll interface. We need to have this facility to cleanup
 * correctly files that are closed without being removed from the eventpoll
 * interface.
 */
static inline void eventpoll_release(struct file *file)
{

	/*
	 * Fast check to avoid the get/release of the semaphore. Since
	 * we're doing this outside the semaphore lock, it might return
	 * false negatives, but we don't care. It'll help in 99.99% of cases
	 * to avoid the semaphore lock. False positives simply cannot happen
	 * because the file in on the way to be removed and nobody ( but
	 * eventpoll ) has still a reference to this file.
	 */
	if (likely(list_empty(&file->f_ep_links)))
		return;

	/*
	 * The file is being closed while it is still linked to an epoll
	 * descriptor. We need to handle this by correctly unlinking it
	 * from its containers.
	 */
	eventpoll_release_file(file);
}

#else

static inline void eventpoll_init_file(struct file *file) {}
static inline void eventpoll_release(struct file *file) {}

#endif

#endif /* #ifndef _LINUX_EVENTPOLL_H */
Commit	Line	Data
2874c5fd	1	/* SPDX-License-Identifier: GPL-2.0-or-later */
1da177e4	2	/*
25985edc	3	* include/linux/eventpoll.h ( Efficient event polling implementation )
3419b23a	4	* Copyright (C) 2001,...,2006 Davide Libenzi
1da177e4	5	*
1da177e4	6	* Davide Libenzi <davidel@xmailserver.org>
1da177e4	7	*/
1da177e4 LT	8	#ifndef _LINUX_EVENTPOLL_H
	9	#define _LINUX_EVENTPOLL_H
	10
607ca46e	11	#include <uapi/linux/eventpoll.h>
0791e364	12	#include <uapi/linux/kcmp.h>
1da177e4	13
1da177e4 LT	14
	15	/* Forward declarations to avoid compiler errors */
	16	struct file;
	17
	18
	19	#ifdef CONFIG_EPOLL
	20
92ef6da3	21	#ifdef CONFIG_CHECKPOINT_RESTORE
0791e364	22	struct file get_epoll_tfile_raw_ptr(struct file file, int tfd, unsigned long toff);
92ef6da3	23	#endif
0791e364	24
1da177e4	25	/* Used to initialize the epoll bits inside the "struct file" */
5a6b7951 BL	26	static inline void eventpoll_init_file(struct file *file)
	27	{
	28	INIT_LIST_HEAD(&file->f_ep_links);
28d82dc1	29	INIT_LIST_HEAD(&file->f_tfile_llink);
5a6b7951 BL	30	}
5a6b7951 BL	31
1da177e4 LT	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	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
1da177e4 LT	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
1da177e4	71	#endif /* #ifndef _LINUX_EVENTPOLL_H */