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342e73b3 JL |
1 | #ifndef _ASM_POWERPC_RWSEM_H |
2 | #define _ASM_POWERPC_RWSEM_H | |
3 | ||
4 | #ifdef __KERNEL__ | |
5 | ||
1da177e4 | 6 | /* |
2ef9481e | 7 | * include/asm-powerpc/rwsem.h: R/W semaphores for PPC using the stuff |
1da177e4 LT |
8 | * in lib/rwsem.c. Adapted largely from include/asm-i386/rwsem.h |
9 | * by Paul Mackerras <paulus@samba.org>. | |
1da177e4 LT |
10 | */ |
11 | ||
1da177e4 LT |
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 | */ | |
20 | struct 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; | |
1da177e4 LT |
31 | }; |
32 | ||
1da177e4 LT |
33 | #define __RWSEM_INITIALIZER(name) \ |
34 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
61f4c3d6 | 35 | LIST_HEAD_INIT((name).wait_list) } |
1da177e4 LT |
36 | |
37 | #define DECLARE_RWSEM(name) \ | |
38 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
39 | ||
40 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
41 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
42 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
43 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
44 | ||
45 | static inline void init_rwsem(struct rw_semaphore *sem) | |
46 | { | |
47 | sem->count = RWSEM_UNLOCKED_VALUE; | |
48 | spin_lock_init(&sem->wait_lock); | |
49 | INIT_LIST_HEAD(&sem->wait_list); | |
1da177e4 LT |
50 | } |
51 | ||
52 | /* | |
53 | * lock for reading | |
54 | */ | |
55 | static inline void __down_read(struct rw_semaphore *sem) | |
56 | { | |
57 | if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0)) | |
58 | rwsem_down_read_failed(sem); | |
59 | } | |
60 | ||
61 | static inline int __down_read_trylock(struct rw_semaphore *sem) | |
62 | { | |
63 | int tmp; | |
64 | ||
65 | while ((tmp = sem->count) >= 0) { | |
66 | if (tmp == cmpxchg(&sem->count, tmp, | |
67 | tmp + RWSEM_ACTIVE_READ_BIAS)) { | |
68 | return 1; | |
69 | } | |
70 | } | |
71 | return 0; | |
72 | } | |
73 | ||
74 | /* | |
75 | * lock for writing | |
76 | */ | |
77 | static inline void __down_write(struct rw_semaphore *sem) | |
78 | { | |
79 | int tmp; | |
80 | ||
81 | tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, | |
82 | (atomic_t *)(&sem->count)); | |
83 | if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) | |
84 | rwsem_down_write_failed(sem); | |
85 | } | |
86 | ||
87 | static inline int __down_write_trylock(struct rw_semaphore *sem) | |
88 | { | |
89 | int tmp; | |
90 | ||
91 | tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, | |
92 | RWSEM_ACTIVE_WRITE_BIAS); | |
93 | return tmp == RWSEM_UNLOCKED_VALUE; | |
94 | } | |
95 | ||
96 | /* | |
97 | * unlock after reading | |
98 | */ | |
99 | static inline void __up_read(struct rw_semaphore *sem) | |
100 | { | |
101 | int tmp; | |
102 | ||
103 | tmp = atomic_dec_return((atomic_t *)(&sem->count)); | |
104 | if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)) | |
105 | rwsem_wake(sem); | |
106 | } | |
107 | ||
108 | /* | |
109 | * unlock after writing | |
110 | */ | |
111 | static inline void __up_write(struct rw_semaphore *sem) | |
112 | { | |
113 | if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, | |
114 | (atomic_t *)(&sem->count)) < 0)) | |
115 | rwsem_wake(sem); | |
116 | } | |
117 | ||
118 | /* | |
119 | * implement atomic add functionality | |
120 | */ | |
121 | static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem) | |
122 | { | |
123 | atomic_add(delta, (atomic_t *)(&sem->count)); | |
124 | } | |
125 | ||
126 | /* | |
127 | * downgrade write lock to read lock | |
128 | */ | |
129 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
130 | { | |
131 | int tmp; | |
132 | ||
133 | tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); | |
134 | if (tmp < 0) | |
135 | rwsem_downgrade_wake(sem); | |
136 | } | |
137 | ||
138 | /* | |
139 | * implement exchange and add functionality | |
140 | */ | |
141 | static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) | |
142 | { | |
143 | return atomic_add_return(delta, (atomic_t *)(&sem->count)); | |
144 | } | |
145 | ||
eb92f4ef RVR |
146 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
147 | { | |
148 | return (sem->count != 0); | |
149 | } | |
150 | ||
342e73b3 JL |
151 | #endif /* __KERNEL__ */ |
152 | #endif /* _ASM_POWERPC_RWSEM_H */ |