1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (c) 2008 Intel Corporation
4 * Author: Matthew Wilcox <willy@linux.intel.com>
5 *
6 * Please see kernel/locking/semaphore.c for documentation of these functions
7 */
8#ifndef __LINUX_SEMAPHORE_H
9#define __LINUX_SEMAPHORE_H
10
11#include <linux/list.h>
12#include <linux/spinlock.h>
13
14/* Please don't access any members of this structure directly */
15struct semaphore {
16	raw_spinlock_t		lock;
17	unsigned int		count;
18	struct list_head	wait_list;
19};
20
21#define __SEMAPHORE_INITIALIZER(name, n)				\
22{									\
23	.lock		= __RAW_SPIN_LOCK_UNLOCKED((name).lock),	\
24	.count		= n,						\
25	.wait_list	= LIST_HEAD_INIT((name).wait_list),		\
26}
27
28/*
29 * Unlike mutexes, binary semaphores do not have an owner, so up() can
30 * be called in a different thread from the one which called down().
31 * It is also safe to call down_trylock() and up() from interrupt
32 * context.
33 */
34#define DEFINE_SEMAPHORE(_name, _n)	\
35	struct semaphore _name = __SEMAPHORE_INITIALIZER(_name, _n)
36
37static inline void sema_init(struct semaphore *sem, int val)
38{
39	static struct lock_class_key __key;
40	*sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
41	lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0);
42}
43
44extern void down(struct semaphore *sem);
45extern int __must_check down_interruptible(struct semaphore *sem);
46extern int __must_check down_killable(struct semaphore *sem);
47extern int __must_check down_trylock(struct semaphore *sem);
48extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
49extern void up(struct semaphore *sem);
50
51#endif /* __LINUX_SEMAPHORE_H */
52