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1#ifndef _ASM_POWERPC_RWSEM_H
2#define _ASM_POWERPC_RWSEM_H
3
4#ifndef _LINUX_RWSEM_H
5#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
6#endif
7
8#ifdef __KERNEL__
9
10/*
11 * include/asm-powerpc/rwsem.h: R/W semaphores for PPC using the stuff
12 * in lib/rwsem.c. Adapted largely from include/asm-i386/rwsem.h
13 * by Paul Mackerras <paulus@samba.org>.
14 */
15
16#include <linux/list.h>
17#include <linux/spinlock.h>
18#include <asm/atomic.h>
19#include <asm/system.h>
20
21/*
22 * the semaphore definition
23 */
24struct rw_semaphore {
25 /* XXX this should be able to be an atomic_t -- paulus */
26 signed int count;
27#define RWSEM_UNLOCKED_VALUE 0x00000000
28#define RWSEM_ACTIVE_BIAS 0x00000001
29#define RWSEM_ACTIVE_MASK 0x0000ffff
30#define RWSEM_WAITING_BIAS (-0x00010000)
31#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
32#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
33 spinlock_t wait_lock;
34 struct list_head wait_list;
35};
36
37#define __RWSEM_INITIALIZER(name) \
38 { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
39 LIST_HEAD_INIT((name).wait_list) }
40
41#define DECLARE_RWSEM(name) \
42 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
43
44extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
45extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
46extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
47extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
48
49static inline void init_rwsem(struct rw_semaphore *sem)
50{
51 sem->count = RWSEM_UNLOCKED_VALUE;
52 spin_lock_init(&sem->wait_lock);
53 INIT_LIST_HEAD(&sem->wait_list);
54}
55
56/*
57 * lock for reading
58 */
59static inline void __down_read(struct rw_semaphore *sem)
60{
61 if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
62 rwsem_down_read_failed(sem);
63}
64
65static inline int __down_read_trylock(struct rw_semaphore *sem)
66{
67 int tmp;
68
69 while ((tmp = sem->count) >= 0) {
70 if (tmp == cmpxchg(&sem->count, tmp,
71 tmp + RWSEM_ACTIVE_READ_BIAS)) {
72 return 1;
73 }
74 }
75 return 0;
76}
77
78/*
79 * lock for writing
80 */
81static inline void __down_write(struct rw_semaphore *sem)
82{
83 int tmp;
84
85 tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
86 (atomic_t *)(&sem->count));
87 if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
88 rwsem_down_write_failed(sem);
89}
90
91static inline int __down_write_trylock(struct rw_semaphore *sem)
92{
93 int tmp;
94
95 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
96 RWSEM_ACTIVE_WRITE_BIAS);
97 return tmp == RWSEM_UNLOCKED_VALUE;
98}
99
100/*
101 * unlock after reading
102 */
103static inline void __up_read(struct rw_semaphore *sem)
104{
105 int tmp;
106
107 tmp = atomic_dec_return((atomic_t *)(&sem->count));
108 if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
109 rwsem_wake(sem);
110}
111
112/*
113 * unlock after writing
114 */
115static inline void __up_write(struct rw_semaphore *sem)
116{
117 if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
118 (atomic_t *)(&sem->count)) < 0))
119 rwsem_wake(sem);
120}
121
122/*
123 * implement atomic add functionality
124 */
125static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
126{
127 atomic_add(delta, (atomic_t *)(&sem->count));
128}
129
130/*
131 * downgrade write lock to read lock
132 */
133static inline void __downgrade_write(struct rw_semaphore *sem)
134{
135 int tmp;
136
137 tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
138 if (tmp < 0)
139 rwsem_downgrade_wake(sem);
140}
141
142/*
143 * implement exchange and add functionality
144 */
145static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
146{
147 return atomic_add_return(delta, (atomic_t *)(&sem->count));
148}
149
150static inline int rwsem_is_locked(struct rw_semaphore *sem)
151{
152 return (sem->count != 0);
153}
154
155#endif /* __KERNEL__ */
156#endif /* _ASM_POWERPC_RWSEM_H */