semaphore.h

 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#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
21	unsigned long		last_holder;
22#endif
23};
24
25#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
26#define __LAST_HOLDER_SEMAPHORE_INITIALIZER				\
27	, .last_holder = 0UL
28#else
29#define __LAST_HOLDER_SEMAPHORE_INITIALIZER
30#endif
31
32#define __SEMAPHORE_INITIALIZER(name, n)				\
33{									\
34	.lock		= __RAW_SPIN_LOCK_UNLOCKED((name).lock),	\
35	.count		= n,						\
36	.wait_list	= LIST_HEAD_INIT((name).wait_list)		\
37	__LAST_HOLDER_SEMAPHORE_INITIALIZER				\
38}
39
40/*
41 * Unlike mutexes, binary semaphores do not have an owner, so up() can
42 * be called in a different thread from the one which called down().
43 * It is also safe to call down_trylock() and up() from interrupt
44 * context.
45 */
46#define DEFINE_SEMAPHORE(_name, _n)	\
47	struct semaphore _name = __SEMAPHORE_INITIALIZER(_name, _n)
48
49static inline void sema_init(struct semaphore *sem, int val)
50{
51	static struct lock_class_key __key;
52	*sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
53	lockdep_init_map(&sem->lock.dep_map, "semaphore->lock", &__key, 0);
54}
55
56extern void down(struct semaphore *sem);
57extern int __must_check down_interruptible(struct semaphore *sem);
58extern int __must_check down_killable(struct semaphore *sem);
59extern int __must_check down_trylock(struct semaphore *sem);
60extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
61extern void up(struct semaphore *sem);
62extern unsigned long sem_last_holder(struct semaphore *sem);
63
64#endif /* __LINUX_SEMAPHORE_H */