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1/* SPDX-License-Identifier: GPL-2.0 */
2/* rwsem-spinlock.h: fallback C implementation
3 *
4 * Copyright (c) 2001 David Howells (dhowells@redhat.com).
5 * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
6 * - Derived also from comments by Linus
7 */
8
9#ifndef _LINUX_RWSEM_SPINLOCK_H
10#define _LINUX_RWSEM_SPINLOCK_H
11
12#ifndef _LINUX_RWSEM_H
13#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
14#endif
15
16#ifdef __KERNEL__
17/*
18 * the rw-semaphore definition
19 * - if count is 0 then there are no active readers or writers
20 * - if count is +ve then that is the number of active readers
21 * - if count is -1 then there is one active writer
22 * - if wait_list is not empty, then there are processes waiting for the semaphore
23 */
24struct rw_semaphore {
25 __s32 count;
26 raw_spinlock_t wait_lock;
27 struct list_head wait_list;
28#ifdef CONFIG_DEBUG_LOCK_ALLOC
29 struct lockdep_map dep_map;
30#endif
31};
32
33#define RWSEM_UNLOCKED_VALUE 0x00000000
34
35extern void __down_read(struct rw_semaphore *sem);
36extern int __must_check __down_read_killable(struct rw_semaphore *sem);
37extern int __down_read_trylock(struct rw_semaphore *sem);
38extern void __down_write(struct rw_semaphore *sem);
39extern int __must_check __down_write_killable(struct rw_semaphore *sem);
40extern int __down_write_trylock(struct rw_semaphore *sem);
41extern void __up_read(struct rw_semaphore *sem);
42extern void __up_write(struct rw_semaphore *sem);
43extern void __downgrade_write(struct rw_semaphore *sem);
44extern int rwsem_is_locked(struct rw_semaphore *sem);
45
46#endif /* __KERNEL__ */
47#endif /* _LINUX_RWSEM_SPINLOCK_H */