Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * include/asm-ppc/rwsem.h: R/W semaphores for SH using the stuff | |
3 | * in lib/rwsem.c. | |
4 | */ | |
5 | ||
6 | #ifndef _ASM_SH_RWSEM_H | |
7 | #define _ASM_SH_RWSEM_H | |
8 | ||
9 | #ifdef __KERNEL__ | |
10 | #include <linux/list.h> | |
11 | #include <linux/spinlock.h> | |
12 | #include <asm/atomic.h> | |
13 | #include <asm/system.h> | |
14 | ||
15 | /* | |
16 | * the semaphore definition | |
17 | */ | |
18 | struct rw_semaphore { | |
19 | long count; | |
20 | #define RWSEM_UNLOCKED_VALUE 0x00000000 | |
21 | #define RWSEM_ACTIVE_BIAS 0x00000001 | |
22 | #define RWSEM_ACTIVE_MASK 0x0000ffff | |
23 | #define RWSEM_WAITING_BIAS (-0x00010000) | |
24 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS | |
25 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
26 | spinlock_t wait_lock; | |
27 | struct list_head wait_list; | |
28 | #if RWSEM_DEBUG | |
29 | int debug; | |
30 | #endif | |
31 | }; | |
32 | ||
33 | /* | |
34 | * initialisation | |
35 | */ | |
36 | #if RWSEM_DEBUG | |
37 | #define __RWSEM_DEBUG_INIT , 0 | |
38 | #else | |
39 | #define __RWSEM_DEBUG_INIT /* */ | |
40 | #endif | |
41 | ||
42 | #define __RWSEM_INITIALIZER(name) \ | |
43 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
44 | LIST_HEAD_INIT((name).wait_list) \ | |
45 | __RWSEM_DEBUG_INIT } | |
46 | ||
47 | #define DECLARE_RWSEM(name) \ | |
48 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
49 | ||
50 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
51 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
52 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
53 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
54 | ||
55 | static inline void init_rwsem(struct rw_semaphore *sem) | |
56 | { | |
57 | sem->count = RWSEM_UNLOCKED_VALUE; | |
58 | spin_lock_init(&sem->wait_lock); | |
59 | INIT_LIST_HEAD(&sem->wait_list); | |
60 | #if RWSEM_DEBUG | |
61 | sem->debug = 0; | |
62 | #endif | |
63 | } | |
64 | ||
65 | /* | |
66 | * lock for reading | |
67 | */ | |
68 | static inline void __down_read(struct rw_semaphore *sem) | |
69 | { | |
70 | if (atomic_inc_return((atomic_t *)(&sem->count)) > 0) | |
71 | smp_wmb(); | |
72 | else | |
73 | rwsem_down_read_failed(sem); | |
74 | } | |
75 | ||
76 | static inline int __down_read_trylock(struct rw_semaphore *sem) | |
77 | { | |
78 | int tmp; | |
79 | ||
80 | while ((tmp = sem->count) >= 0) { | |
81 | if (tmp == cmpxchg(&sem->count, tmp, | |
82 | tmp + RWSEM_ACTIVE_READ_BIAS)) { | |
83 | smp_wmb(); | |
84 | return 1; | |
85 | } | |
86 | } | |
87 | return 0; | |
88 | } | |
89 | ||
90 | /* | |
91 | * lock for writing | |
92 | */ | |
93 | static 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 (tmp == RWSEM_ACTIVE_WRITE_BIAS) | |
100 | smp_wmb(); | |
101 | else | |
102 | rwsem_down_write_failed(sem); | |
103 | } | |
104 | ||
105 | static inline int __down_write_trylock(struct rw_semaphore *sem) | |
106 | { | |
107 | int tmp; | |
108 | ||
109 | tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, | |
110 | RWSEM_ACTIVE_WRITE_BIAS); | |
111 | smp_wmb(); | |
112 | return tmp == RWSEM_UNLOCKED_VALUE; | |
113 | } | |
114 | ||
115 | /* | |
116 | * unlock after reading | |
117 | */ | |
118 | static inline void __up_read(struct rw_semaphore *sem) | |
119 | { | |
120 | int tmp; | |
121 | ||
122 | smp_wmb(); | |
123 | tmp = atomic_dec_return((atomic_t *)(&sem->count)); | |
124 | if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) | |
125 | rwsem_wake(sem); | |
126 | } | |
127 | ||
128 | /* | |
129 | * unlock after writing | |
130 | */ | |
131 | static inline void __up_write(struct rw_semaphore *sem) | |
132 | { | |
133 | smp_wmb(); | |
134 | if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, | |
135 | (atomic_t *)(&sem->count)) < 0) | |
136 | rwsem_wake(sem); | |
137 | } | |
138 | ||
139 | /* | |
140 | * implement atomic add functionality | |
141 | */ | |
142 | static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem) | |
143 | { | |
144 | atomic_add(delta, (atomic_t *)(&sem->count)); | |
145 | } | |
146 | ||
147 | /* | |
148 | * downgrade write lock to read lock | |
149 | */ | |
150 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
151 | { | |
152 | int tmp; | |
153 | ||
154 | smp_wmb(); | |
155 | tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); | |
156 | if (tmp < 0) | |
157 | rwsem_downgrade_wake(sem); | |
158 | } | |
159 | ||
160 | /* | |
161 | * implement exchange and add functionality | |
162 | */ | |
163 | static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) | |
164 | { | |
165 | smp_mb(); | |
166 | return atomic_add_return(delta, (atomic_t *)(&sem->count)); | |
167 | } | |
168 | ||
169 | #endif /* __KERNEL__ */ | |
170 | #endif /* _ASM_SH_RWSEM_H */ |