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 */
15 struct 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
37 static 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
44 extern void down(struct semaphore *sem);
45 extern int __must_check down_interruptible(struct semaphore *sem);
46 extern int __must_check down_killable(struct semaphore *sem);
47 extern int __must_check down_trylock(struct semaphore *sem);
48 extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
49 extern void up(struct semaphore *sem);
50
51 #endif /* __LINUX_SEMAPHORE_H */
52
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