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1da177e4 LT |
1 | /* |
2 | * include/asm-ppc/rwsem.h: R/W semaphores for PPC using the stuff | |
3 | * in lib/rwsem.c. Adapted largely from include/asm-i386/rwsem.h | |
4 | * by Paul Mackerras <paulus@samba.org>. | |
5 | */ | |
6 | ||
7 | #ifndef _PPC_RWSEM_H | |
8 | #define _PPC_RWSEM_H | |
9 | ||
10 | #ifdef __KERNEL__ | |
11 | #include <linux/list.h> | |
12 | #include <linux/spinlock.h> | |
13 | #include <asm/atomic.h> | |
14 | #include <asm/system.h> | |
15 | ||
16 | /* | |
17 | * the semaphore definition | |
18 | */ | |
19 | struct rw_semaphore { | |
20 | /* XXX this should be able to be an atomic_t -- paulus */ | |
21 | signed long count; | |
22 | #define RWSEM_UNLOCKED_VALUE 0x00000000 | |
23 | #define RWSEM_ACTIVE_BIAS 0x00000001 | |
24 | #define RWSEM_ACTIVE_MASK 0x0000ffff | |
25 | #define RWSEM_WAITING_BIAS (-0x00010000) | |
26 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS | |
27 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
28 | spinlock_t wait_lock; | |
29 | struct list_head wait_list; | |
30 | #if RWSEM_DEBUG | |
31 | int debug; | |
32 | #endif | |
33 | }; | |
34 | ||
35 | /* | |
36 | * initialisation | |
37 | */ | |
38 | #if RWSEM_DEBUG | |
39 | #define __RWSEM_DEBUG_INIT , 0 | |
40 | #else | |
41 | #define __RWSEM_DEBUG_INIT /* */ | |
42 | #endif | |
43 | ||
44 | #define __RWSEM_INITIALIZER(name) \ | |
45 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
46 | LIST_HEAD_INIT((name).wait_list) \ | |
47 | __RWSEM_DEBUG_INIT } | |
48 | ||
49 | #define DECLARE_RWSEM(name) \ | |
50 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
51 | ||
52 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
53 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
54 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
55 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
56 | ||
57 | static inline void init_rwsem(struct rw_semaphore *sem) | |
58 | { | |
59 | sem->count = RWSEM_UNLOCKED_VALUE; | |
60 | spin_lock_init(&sem->wait_lock); | |
61 | INIT_LIST_HEAD(&sem->wait_list); | |
62 | #if RWSEM_DEBUG | |
63 | sem->debug = 0; | |
64 | #endif | |
65 | } | |
66 | ||
67 | /* | |
68 | * lock for reading | |
69 | */ | |
70 | static inline void __down_read(struct rw_semaphore *sem) | |
71 | { | |
72 | if (atomic_inc_return((atomic_t *)(&sem->count)) > 0) | |
73 | smp_wmb(); | |
74 | else | |
75 | rwsem_down_read_failed(sem); | |
76 | } | |
77 | ||
78 | static inline int __down_read_trylock(struct rw_semaphore *sem) | |
79 | { | |
80 | int tmp; | |
81 | ||
82 | while ((tmp = sem->count) >= 0) { | |
83 | if (tmp == cmpxchg(&sem->count, tmp, | |
84 | tmp + RWSEM_ACTIVE_READ_BIAS)) { | |
85 | smp_wmb(); | |
86 | return 1; | |
87 | } | |
88 | } | |
89 | return 0; | |
90 | } | |
91 | ||
92 | /* | |
93 | * lock for writing | |
94 | */ | |
95 | static inline void __down_write(struct rw_semaphore *sem) | |
96 | { | |
97 | int tmp; | |
98 | ||
99 | tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, | |
100 | (atomic_t *)(&sem->count)); | |
101 | if (tmp == RWSEM_ACTIVE_WRITE_BIAS) | |
102 | smp_wmb(); | |
103 | else | |
104 | rwsem_down_write_failed(sem); | |
105 | } | |
106 | ||
107 | static inline int __down_write_trylock(struct rw_semaphore *sem) | |
108 | { | |
109 | int tmp; | |
110 | ||
111 | tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, | |
112 | RWSEM_ACTIVE_WRITE_BIAS); | |
113 | smp_wmb(); | |
114 | return tmp == RWSEM_UNLOCKED_VALUE; | |
115 | } | |
116 | ||
117 | /* | |
118 | * unlock after reading | |
119 | */ | |
120 | static inline void __up_read(struct rw_semaphore *sem) | |
121 | { | |
122 | int tmp; | |
123 | ||
124 | smp_wmb(); | |
125 | tmp = atomic_dec_return((atomic_t *)(&sem->count)); | |
126 | if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) | |
127 | rwsem_wake(sem); | |
128 | } | |
129 | ||
130 | /* | |
131 | * unlock after writing | |
132 | */ | |
133 | static inline void __up_write(struct rw_semaphore *sem) | |
134 | { | |
135 | smp_wmb(); | |
136 | if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, | |
137 | (atomic_t *)(&sem->count)) < 0) | |
138 | rwsem_wake(sem); | |
139 | } | |
140 | ||
141 | /* | |
142 | * implement atomic add functionality | |
143 | */ | |
144 | static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem) | |
145 | { | |
146 | atomic_add(delta, (atomic_t *)(&sem->count)); | |
147 | } | |
148 | ||
149 | /* | |
150 | * downgrade write lock to read lock | |
151 | */ | |
152 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
153 | { | |
154 | int tmp; | |
155 | ||
156 | smp_wmb(); | |
157 | tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); | |
158 | if (tmp < 0) | |
159 | rwsem_downgrade_wake(sem); | |
160 | } | |
161 | ||
162 | /* | |
163 | * implement exchange and add functionality | |
164 | */ | |
165 | static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) | |
166 | { | |
167 | smp_mb(); | |
168 | return atomic_add_return(delta, (atomic_t *)(&sem->count)); | |
169 | } | |
170 | ||
171 | #endif /* __KERNEL__ */ | |
172 | #endif /* _PPC_RWSEM_XADD_H */ |