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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, LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
48
49#define DECLARE_RWSEM(name) \
50 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
51
52extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
53 struct lock_class_key *key);
54
55#define init_rwsem(sem) \
56do { \
57 static struct lock_class_key __key; \
58 \
59 __init_rwsem((sem), #sem, &__key); \
60} while (0)
61
62extern void FASTCALL(__down_read(struct rw_semaphore *sem));
63extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
64extern void FASTCALL(__down_write(struct rw_semaphore *sem));
65extern void FASTCALL(__down_write_nested(struct rw_semaphore *sem, int subclass));
66extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
67extern void FASTCALL(__up_read(struct rw_semaphore *sem));
68extern void FASTCALL(__up_write(struct rw_semaphore *sem));
69extern void FASTCALL(__downgrade_write(struct rw_semaphore *sem));
70
71static inline int rwsem_is_locked(struct rw_semaphore *sem)
72{
73 return (sem->activity != 0);
74}
75
76#endif /* __KERNEL__ */
77#endif /* _LINUX_RWSEM_SPINLOCK_H */