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 */
65