rwsem-spinlock.h revision c16a87ce063f79e0ec7d25ce2950e1bc6db03c72 
1/* rwsem-spinlock.h: fallback C implementation
2 *
3 * Copyright (c) 2001   David Howells (dhowells@redhat.com).
4 * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
5 * - Derived also from comments by Linus
6 */
7
8#ifndef _LINUX_RWSEM_SPINLOCK_H
9#define _LINUX_RWSEM_SPINLOCK_H
10
11#ifndef _LINUX_RWSEM_H
12#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
13#endif
14
15#ifdef __KERNEL__
16/*
17 * the rw-semaphore definition
18 * - if activity is 0 then there are no active readers or writers
19 * - if activity is +ve then that is the number of active readers
20 * - if activity is -1 then there is one active writer
21 * - if wait_list is not empty, then there are processes waiting for the semaphore
22 */
23struct rw_semaphore {
24	__s32			activity;
25	spinlock_t		wait_lock;
26	struct list_head	wait_list;
27#ifdef CONFIG_DEBUG_LOCK_ALLOC
28	struct lockdep_map dep_map;
29#endif
30};
31
32#ifdef CONFIG_DEBUG_LOCK_ALLOC
33# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
34#else
35# define __RWSEM_DEP_MAP_INIT(lockname)
36#endif
37
38#define __RWSEM_INITIALIZER(name) \
39{ 0, __SPIN_LOCK_UNLOCKED(name.wait_lock), LIST_HEAD_INIT((name).wait_list) \
40  __RWSEM_DEP_MAP_INIT(name) }
41
42#define DECLARE_RWSEM(name) \
43	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
44
45extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
46			 struct lock_class_key *key);
47
48#define init_rwsem(sem)						\
49do {								\
50	static struct lock_class_key __key;			\
51								\
52	__init_rwsem((sem), #sem, &__key);			\
53} while (0)
54
55extern void __down_read(struct rw_semaphore *sem);
56extern int __down_read_trylock(struct rw_semaphore *sem);
57extern void __down_write(struct rw_semaphore *sem);
58extern void __down_write_nested(struct rw_semaphore *sem, int subclass);
59extern int __down_write_trylock(struct rw_semaphore *sem);
60extern void __up_read(struct rw_semaphore *sem);
61extern void __up_write(struct rw_semaphore *sem);
62extern void __downgrade_write(struct rw_semaphore *sem);
63extern int rwsem_is_locked(struct rw_semaphore *sem);
64
65#endif /* __KERNEL__ */
66#endif /* _LINUX_RWSEM_SPINLOCK_H */
67