rwsem-spinlock.h revision 6cfd76a26d9fe2ba54b9d496a48c1d9285e5c5ed 
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#include <linux/spinlock.h>
16#include <linux/list.h>
17
18#ifdef __KERNEL__
19
20#include <linux/types.h>
21
22struct rwsem_waiter;
23
24/*
25 * the rw-semaphore definition
26 * - if activity is 0 then there are no active readers or writers
27 * - if activity is +ve then that is the number of active readers
28 * - if activity is -1 then there is one active writer
29 * - if wait_list is not empty, then there are processes waiting for the semaphore
30 */
31struct rw_semaphore {
32	__s32			activity;
33	spinlock_t		wait_lock;
34	struct list_head	wait_list;
35#ifdef CONFIG_DEBUG_LOCK_ALLOC
36	struct lockdep_map dep_map;
37#endif
38};
39
40#ifdef CONFIG_DEBUG_LOCK_ALLOC
41# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
42#else
43# define __RWSEM_DEP_MAP_INIT(lockname)
44#endif
45
46#define __RWSEM_INITIALIZER(name) \
47{ 0, __SPIN_LOCK_UNLOCKED(name.wait_lock), LIST_HEAD_INIT((name).wait_list) \
48  __RWSEM_DEP_MAP_INIT(name) }
49
50#define DECLARE_RWSEM(name) \
51	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
52
53extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
54			 struct lock_class_key *key);
55
56#define init_rwsem(sem)						\
57do {								\
58	static struct lock_class_key __key;			\
59								\
60	__init_rwsem((sem), #sem, &__key);			\
61} while (0)
62
63extern void FASTCALL(__down_read(struct rw_semaphore *sem));
64extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
65extern void FASTCALL(__down_write(struct rw_semaphore *sem));
66extern void FASTCALL(__down_write_nested(struct rw_semaphore *sem, int subclass));
67extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
68extern void FASTCALL(__up_read(struct rw_semaphore *sem));
69extern void FASTCALL(__up_write(struct rw_semaphore *sem));
70extern void FASTCALL(__downgrade_write(struct rw_semaphore *sem));
71
72static inline int rwsem_is_locked(struct rw_semaphore *sem)
73{
74	return (sem->activity != 0);
75}
76
77#endif /* __KERNEL__ */
78#endif /* _LINUX_RWSEM_SPINLOCK_H */
79