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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 | ||
14ac12de RD |
16 | #ifndef _LINUX_RWSEM_H |
17 | #error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead." | |
18 | #endif | |
19 | ||
9a8fd558 CZ |
20 | #include <linux/list.h> |
21 | #include <linux/spinlock.h> | |
22 | #include <asm/atomic.h> | |
23 | #include <asm/system.h> | |
24 | ||
25 | /* | |
26 | * the semaphore definition | |
27 | */ | |
28 | struct rw_semaphore { | |
29 | signed long count; | |
30 | #define RWSEM_UNLOCKED_VALUE 0x00000000 | |
31 | #define RWSEM_ACTIVE_BIAS 0x00000001 | |
32 | #define RWSEM_ACTIVE_MASK 0x0000ffff | |
33 | #define RWSEM_WAITING_BIAS (-0x00010000) | |
34 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS | |
35 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
36 | spinlock_t wait_lock; | |
37 | struct list_head wait_list; | |
9a8fd558 CZ |
38 | }; |
39 | ||
9a8fd558 CZ |
40 | #define __RWSEM_INITIALIZER(name) \ |
41 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
61f4c3d6 | 42 | LIST_HEAD_INIT((name).wait_list) } |
9a8fd558 CZ |
43 | |
44 | #define DECLARE_RWSEM(name) \ | |
45 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
46 | ||
47 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
48 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
49 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
50 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
51 | ||
52 | static inline void init_rwsem(struct rw_semaphore *sem) | |
53 | { | |
54 | sem->count = RWSEM_UNLOCKED_VALUE; | |
55 | spin_lock_init(&sem->wait_lock); | |
56 | INIT_LIST_HEAD(&sem->wait_list); | |
9a8fd558 CZ |
57 | } |
58 | ||
59 | /* | |
60 | * lock for reading | |
61 | */ | |
62 | static inline void __down_read(struct rw_semaphore *sem) | |
63 | { | |
64 | if (atomic_add_return(1,(atomic_t *)(&sem->count)) > 0) | |
65 | smp_wmb(); | |
66 | else | |
67 | rwsem_down_read_failed(sem); | |
68 | } | |
69 | ||
70 | static inline int __down_read_trylock(struct rw_semaphore *sem) | |
71 | { | |
72 | int tmp; | |
73 | ||
74 | while ((tmp = sem->count) >= 0) { | |
75 | if (tmp == cmpxchg(&sem->count, tmp, | |
76 | tmp + RWSEM_ACTIVE_READ_BIAS)) { | |
77 | smp_wmb(); | |
78 | return 1; | |
79 | } | |
80 | } | |
81 | return 0; | |
82 | } | |
83 | ||
84 | /* | |
85 | * lock for writing | |
86 | */ | |
87 | static inline void __down_write(struct rw_semaphore *sem) | |
88 | { | |
89 | int tmp; | |
90 | ||
91 | tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, | |
92 | (atomic_t *)(&sem->count)); | |
93 | if (tmp == RWSEM_ACTIVE_WRITE_BIAS) | |
94 | smp_wmb(); | |
95 | else | |
96 | rwsem_down_write_failed(sem); | |
97 | } | |
98 | ||
99 | static inline int __down_write_trylock(struct rw_semaphore *sem) | |
100 | { | |
101 | int tmp; | |
102 | ||
103 | tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, | |
104 | RWSEM_ACTIVE_WRITE_BIAS); | |
105 | smp_wmb(); | |
106 | return tmp == RWSEM_UNLOCKED_VALUE; | |
107 | } | |
108 | ||
109 | /* | |
110 | * unlock after reading | |
111 | */ | |
112 | static inline void __up_read(struct rw_semaphore *sem) | |
113 | { | |
114 | int tmp; | |
115 | ||
116 | smp_wmb(); | |
117 | tmp = atomic_sub_return(1,(atomic_t *)(&sem->count)); | |
118 | if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) | |
119 | rwsem_wake(sem); | |
120 | } | |
121 | ||
122 | /* | |
123 | * unlock after writing | |
124 | */ | |
125 | static inline void __up_write(struct rw_semaphore *sem) | |
126 | { | |
127 | smp_wmb(); | |
128 | if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, | |
129 | (atomic_t *)(&sem->count)) < 0) | |
130 | rwsem_wake(sem); | |
131 | } | |
132 | ||
133 | /* | |
134 | * implement atomic add functionality | |
135 | */ | |
136 | static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem) | |
137 | { | |
138 | atomic_add(delta, (atomic_t *)(&sem->count)); | |
139 | } | |
140 | ||
141 | /* | |
142 | * downgrade write lock to read lock | |
143 | */ | |
144 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
145 | { | |
146 | int tmp; | |
147 | ||
148 | smp_wmb(); | |
149 | tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); | |
150 | if (tmp < 0) | |
151 | rwsem_downgrade_wake(sem); | |
152 | } | |
153 | ||
154 | /* | |
155 | * implement exchange and add functionality | |
156 | */ | |
157 | static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) | |
158 | { | |
159 | smp_mb(); | |
160 | return atomic_add_return(delta, (atomic_t *)(&sem->count)); | |
161 | } | |
162 | ||
b9e122c8 JJ |
163 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
164 | { | |
165 | return (sem->count != 0); | |
166 | } | |
167 | ||
168 | #endif /* _XTENSA_RWSEM_H */ |