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1#ifndef _ASM_POWERPC_RWSEM_H
2#define _ASM_POWERPC_RWSEM_H
3
4#ifdef __KERNEL__
5
6/*
7 * include/asm-ppc64/rwsem.h: R/W semaphores for PPC using the stuff
8 * in lib/rwsem.c. Adapted largely from include/asm-i386/rwsem.h
9 * by Paul Mackerras <paulus@samba.org>.
10 */
11
12#include <linux/list.h>
13#include <linux/spinlock.h>
14#include <asm/atomic.h>
15#include <asm/system.h>
16
17/*
18 * the semaphore definition
19 */
20struct rw_semaphore {
21 /* XXX this should be able to be an atomic_t -- paulus */
22 signed int count;
23#define RWSEM_UNLOCKED_VALUE 0x00000000
24#define RWSEM_ACTIVE_BIAS 0x00000001
25#define RWSEM_ACTIVE_MASK 0x0000ffff
26#define RWSEM_WAITING_BIAS (-0x00010000)
27#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
28#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
29 spinlock_t wait_lock;
30 struct list_head wait_list;
31#if RWSEM_DEBUG
32 int debug;
33#endif
34};
35
36/*
37 * initialisation
38 */
39#if RWSEM_DEBUG
40#define __RWSEM_DEBUG_INIT , 0
41#else
42#define __RWSEM_DEBUG_INIT /* */
43#endif
44
45#define __RWSEM_INITIALIZER(name) \
46 { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
47 LIST_HEAD_INIT((name).wait_list) \
48 __RWSEM_DEBUG_INIT }
49
50#define DECLARE_RWSEM(name) \
51 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
52
53extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
54extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
55extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
56extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
57
58static inline void init_rwsem(struct rw_semaphore *sem)
59{
60 sem->count = RWSEM_UNLOCKED_VALUE;
61 spin_lock_init(&sem->wait_lock);
62 INIT_LIST_HEAD(&sem->wait_list);
63#if RWSEM_DEBUG
64 sem->debug = 0;
65#endif
66}
67
68/*
69 * lock for reading
70 */
71static inline void __down_read(struct rw_semaphore *sem)
72{
73 if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
74 rwsem_down_read_failed(sem);
75}
76
77static inline int __down_read_trylock(struct rw_semaphore *sem)
78{
79 int tmp;
80
81 while ((tmp = sem->count) >= 0) {
82 if (tmp == cmpxchg(&sem->count, tmp,
83 tmp + RWSEM_ACTIVE_READ_BIAS)) {
84 return 1;
85 }
86 }
87 return 0;
88}
89
90/*
91 * lock for writing
92 */
93static inline void __down_write(struct rw_semaphore *sem)
94{
95 int tmp;
96
97 tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
98 (atomic_t *)(&sem->count));
99 if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
100 rwsem_down_write_failed(sem);
101}
102
103static inline int __down_write_trylock(struct rw_semaphore *sem)
104{
105 int tmp;
106
107 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
108 RWSEM_ACTIVE_WRITE_BIAS);
109 return tmp == RWSEM_UNLOCKED_VALUE;
110}
111
112/*
113 * unlock after reading
114 */
115static inline void __up_read(struct rw_semaphore *sem)
116{
117 int tmp;
118
119 tmp = atomic_dec_return((atomic_t *)(&sem->count));
120 if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
121 rwsem_wake(sem);
122}
123
124/*
125 * unlock after writing
126 */
127static inline void __up_write(struct rw_semaphore *sem)
128{
129 if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
130 (atomic_t *)(&sem->count)) < 0))
131 rwsem_wake(sem);
132}
133
134/*
135 * implement atomic add functionality
136 */
137static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
138{
139 atomic_add(delta, (atomic_t *)(&sem->count));
140}
141
142/*
143 * downgrade write lock to read lock
144 */
145static inline void __downgrade_write(struct rw_semaphore *sem)
146{
147 int tmp;
148
149 tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
150 if (tmp < 0)
151 rwsem_downgrade_wake(sem);
152}
153
154/*
155 * implement exchange and add functionality
156 */
157static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
158{
159 return atomic_add_return(delta, (atomic_t *)(&sem->count));
160}
161
162static inline int rwsem_is_locked(struct rw_semaphore *sem)
163{
164 return (sem->count != 0);
165}
166
167#endif /* __KERNEL__ */
168#endif /* _ASM_POWERPC_RWSEM_H */