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9a8fd558 CZ |
1 | /* |
2 | * include/asm-xtensa/rwsem.h | |
3 | * | |
4 | * This file is subject to the terms and conditions of the GNU General Public | |
5 | * License. See the file "COPYING" in the main directory of this archive | |
6 | * for more details. | |
7 | * | |
8 | * Largely copied from include/asm-ppc/rwsem.h | |
9 | * | |
10 | * Copyright (C) 2001 - 2005 Tensilica Inc. | |
11 | */ | |
12 | ||
13 | #ifndef _XTENSA_RWSEM_H | |
14 | #define _XTENSA_RWSEM_H | |
15 | ||
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 | signed long count; | |
26 | #define RWSEM_UNLOCKED_VALUE 0x00000000 | |
27 | #define RWSEM_ACTIVE_BIAS 0x00000001 | |
28 | #define RWSEM_ACTIVE_MASK 0x0000ffff | |
29 | #define RWSEM_WAITING_BIAS (-0x00010000) | |
30 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS | |
31 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
32 | spinlock_t wait_lock; | |
33 | struct list_head wait_list; | |
9a8fd558 CZ |
34 | }; |
35 | ||
9a8fd558 CZ |
36 | #define __RWSEM_INITIALIZER(name) \ |
37 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
61f4c3d6 | 38 | LIST_HEAD_INIT((name).wait_list) } |
9a8fd558 CZ |
39 | |
40 | #define DECLARE_RWSEM(name) \ | |
41 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
42 | ||
43 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
44 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
45 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
46 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
47 | ||
48 | static inline void init_rwsem(struct rw_semaphore *sem) | |
49 | { | |
50 | sem->count = RWSEM_UNLOCKED_VALUE; | |
51 | spin_lock_init(&sem->wait_lock); | |
52 | INIT_LIST_HEAD(&sem->wait_list); | |
9a8fd558 CZ |
53 | } |
54 | ||
55 | /* | |
56 | * lock for reading | |
57 | */ | |
58 | static inline void __down_read(struct rw_semaphore *sem) | |
59 | { | |
60 | if (atomic_add_return(1,(atomic_t *)(&sem->count)) > 0) | |
61 | smp_wmb(); | |
62 | else | |
63 | rwsem_down_read_failed(sem); | |
64 | } | |
65 | ||
66 | static inline int __down_read_trylock(struct rw_semaphore *sem) | |
67 | { | |
68 | int tmp; | |
69 | ||
70 | while ((tmp = sem->count) >= 0) { | |
71 | if (tmp == cmpxchg(&sem->count, tmp, | |
72 | tmp + RWSEM_ACTIVE_READ_BIAS)) { | |
73 | smp_wmb(); | |
74 | return 1; | |
75 | } | |
76 | } | |
77 | return 0; | |
78 | } | |
79 | ||
80 | /* | |
81 | * lock for writing | |
82 | */ | |
83 | static inline void __down_write(struct rw_semaphore *sem) | |
84 | { | |
85 | int tmp; | |
86 | ||
87 | tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, | |
88 | (atomic_t *)(&sem->count)); | |
89 | if (tmp == RWSEM_ACTIVE_WRITE_BIAS) | |
90 | smp_wmb(); | |
91 | else | |
92 | rwsem_down_write_failed(sem); | |
93 | } | |
94 | ||
95 | static inline int __down_write_trylock(struct rw_semaphore *sem) | |
96 | { | |
97 | int tmp; | |
98 | ||
99 | tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, | |
100 | RWSEM_ACTIVE_WRITE_BIAS); | |
101 | smp_wmb(); | |
102 | return tmp == RWSEM_UNLOCKED_VALUE; | |
103 | } | |
104 | ||
105 | /* | |
106 | * unlock after reading | |
107 | */ | |
108 | static inline void __up_read(struct rw_semaphore *sem) | |
109 | { | |
110 | int tmp; | |
111 | ||
112 | smp_wmb(); | |
113 | tmp = atomic_sub_return(1,(atomic_t *)(&sem->count)); | |
114 | if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) | |
115 | rwsem_wake(sem); | |
116 | } | |
117 | ||
118 | /* | |
119 | * unlock after writing | |
120 | */ | |
121 | static inline void __up_write(struct rw_semaphore *sem) | |
122 | { | |
123 | smp_wmb(); | |
124 | if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, | |
125 | (atomic_t *)(&sem->count)) < 0) | |
126 | rwsem_wake(sem); | |
127 | } | |
128 | ||
129 | /* | |
130 | * implement atomic add functionality | |
131 | */ | |
132 | static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem) | |
133 | { | |
134 | atomic_add(delta, (atomic_t *)(&sem->count)); | |
135 | } | |
136 | ||
137 | /* | |
138 | * downgrade write lock to read lock | |
139 | */ | |
140 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
141 | { | |
142 | int tmp; | |
143 | ||
144 | smp_wmb(); | |
145 | tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); | |
146 | if (tmp < 0) | |
147 | rwsem_downgrade_wake(sem); | |
148 | } | |
149 | ||
150 | /* | |
151 | * implement exchange and add functionality | |
152 | */ | |
153 | static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) | |
154 | { | |
155 | smp_mb(); | |
156 | return atomic_add_return(delta, (atomic_t *)(&sem->count)); | |
157 | } | |
158 | ||
b9e122c8 JJ |
159 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
160 | { | |
161 | return (sem->count != 0); | |
162 | } | |
163 | ||
164 | #endif /* _XTENSA_RWSEM_H */ |