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342e73b3 JL |
1 | #ifndef _ASM_POWERPC_RWSEM_H |
2 | #define _ASM_POWERPC_RWSEM_H | |
3 | ||
20b31b53 RD |
4 | #ifndef _LINUX_RWSEM_H |
5 | #error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead." | |
6 | #endif | |
7 | ||
342e73b3 JL |
8 | #ifdef __KERNEL__ |
9 | ||
1da177e4 | 10 | /* |
2ef9481e | 11 | * include/asm-powerpc/rwsem.h: R/W semaphores for PPC using the stuff |
1da177e4 LT |
12 | * in lib/rwsem.c. Adapted largely from include/asm-i386/rwsem.h |
13 | * by Paul Mackerras <paulus@samba.org>. | |
1da177e4 LT |
14 | */ |
15 | ||
1da177e4 LT |
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 | */ | |
24 | struct 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; | |
1da177e4 LT |
35 | }; |
36 | ||
1da177e4 LT |
37 | #define __RWSEM_INITIALIZER(name) \ |
38 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
61f4c3d6 | 39 | LIST_HEAD_INIT((name).wait_list) } |
1da177e4 LT |
40 | |
41 | #define DECLARE_RWSEM(name) \ | |
42 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
43 | ||
44 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
45 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
46 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
47 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
48 | ||
49 | static 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); | |
1da177e4 LT |
54 | } |
55 | ||
56 | /* | |
57 | * lock for reading | |
58 | */ | |
59 | static 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 | ||
65 | static 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 | */ | |
81 | static 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 | ||
91 | static 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 | */ | |
103 | static 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 | */ | |
115 | static 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 | */ | |
125 | static 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 | */ | |
133 | static 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 | */ | |
145 | static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) | |
146 | { | |
147 | return atomic_add_return(delta, (atomic_t *)(&sem->count)); | |
148 | } | |
149 | ||
eb92f4ef RVR |
150 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
151 | { | |
152 | return (sem->count != 0); | |
153 | } | |
154 | ||
342e73b3 JL |
155 | #endif /* __KERNEL__ */ |
156 | #endif /* _ASM_POWERPC_RWSEM_H */ |