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1da177e4 LT |
1 | #ifndef _ALPHA_RWSEM_H |
2 | #define _ALPHA_RWSEM_H | |
3 | ||
4 | /* | |
5 | * Written by Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 2001. | |
6 | * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h | |
7 | */ | |
8 | ||
9 | #ifndef _LINUX_RWSEM_H | |
10 | #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead" | |
11 | #endif | |
12 | ||
13 | #ifdef __KERNEL__ | |
14 | ||
15 | #include <linux/compiler.h> | |
16 | #include <linux/list.h> | |
17 | #include <linux/spinlock.h> | |
18 | ||
19 | struct rwsem_waiter; | |
20 | ||
21 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
22 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
23 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *); | |
24 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
25 | ||
26 | /* | |
27 | * the semaphore definition | |
28 | */ | |
29 | struct rw_semaphore { | |
30 | long count; | |
31 | #define RWSEM_UNLOCKED_VALUE 0x0000000000000000L | |
32 | #define RWSEM_ACTIVE_BIAS 0x0000000000000001L | |
33 | #define RWSEM_ACTIVE_MASK 0x00000000ffffffffL | |
34 | #define RWSEM_WAITING_BIAS (-0x0000000100000000L) | |
35 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS | |
36 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
37 | spinlock_t wait_lock; | |
38 | struct list_head wait_list; | |
1da177e4 LT |
39 | }; |
40 | ||
1da177e4 LT |
41 | #define __RWSEM_INITIALIZER(name) \ |
42 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
61f4c3d6 | 43 | LIST_HEAD_INIT((name).wait_list) } |
1da177e4 LT |
44 | |
45 | #define DECLARE_RWSEM(name) \ | |
46 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
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); | |
1da177e4 LT |
53 | } |
54 | ||
55 | static inline void __down_read(struct rw_semaphore *sem) | |
56 | { | |
57 | long oldcount; | |
58 | #ifndef CONFIG_SMP | |
59 | oldcount = sem->count; | |
60 | sem->count += RWSEM_ACTIVE_READ_BIAS; | |
61 | #else | |
62 | long temp; | |
63 | __asm__ __volatile__( | |
64 | "1: ldq_l %0,%1\n" | |
65 | " addq %0,%3,%2\n" | |
66 | " stq_c %2,%1\n" | |
67 | " beq %2,2f\n" | |
68 | " mb\n" | |
69 | ".subsection 2\n" | |
70 | "2: br 1b\n" | |
71 | ".previous" | |
72 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
73 | :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory"); | |
74 | #endif | |
75 | if (unlikely(oldcount < 0)) | |
76 | rwsem_down_read_failed(sem); | |
77 | } | |
78 | ||
79 | /* | |
80 | * trylock for reading -- returns 1 if successful, 0 if contention | |
81 | */ | |
82 | static inline int __down_read_trylock(struct rw_semaphore *sem) | |
83 | { | |
84 | long old, new, res; | |
85 | ||
86 | res = sem->count; | |
87 | do { | |
88 | new = res + RWSEM_ACTIVE_READ_BIAS; | |
89 | if (new <= 0) | |
90 | break; | |
91 | old = res; | |
92 | res = cmpxchg(&sem->count, old, new); | |
93 | } while (res != old); | |
94 | return res >= 0 ? 1 : 0; | |
95 | } | |
96 | ||
97 | static inline void __down_write(struct rw_semaphore *sem) | |
98 | { | |
99 | long oldcount; | |
100 | #ifndef CONFIG_SMP | |
101 | oldcount = sem->count; | |
102 | sem->count += RWSEM_ACTIVE_WRITE_BIAS; | |
103 | #else | |
104 | long temp; | |
105 | __asm__ __volatile__( | |
106 | "1: ldq_l %0,%1\n" | |
107 | " addq %0,%3,%2\n" | |
108 | " stq_c %2,%1\n" | |
109 | " beq %2,2f\n" | |
110 | " mb\n" | |
111 | ".subsection 2\n" | |
112 | "2: br 1b\n" | |
113 | ".previous" | |
114 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
115 | :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory"); | |
116 | #endif | |
117 | if (unlikely(oldcount)) | |
118 | rwsem_down_write_failed(sem); | |
119 | } | |
120 | ||
121 | /* | |
122 | * trylock for writing -- returns 1 if successful, 0 if contention | |
123 | */ | |
124 | static inline int __down_write_trylock(struct rw_semaphore *sem) | |
125 | { | |
126 | long ret = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, | |
127 | RWSEM_ACTIVE_WRITE_BIAS); | |
128 | if (ret == RWSEM_UNLOCKED_VALUE) | |
129 | return 1; | |
130 | return 0; | |
131 | } | |
132 | ||
133 | static inline void __up_read(struct rw_semaphore *sem) | |
134 | { | |
135 | long oldcount; | |
136 | #ifndef CONFIG_SMP | |
137 | oldcount = sem->count; | |
138 | sem->count -= RWSEM_ACTIVE_READ_BIAS; | |
139 | #else | |
140 | long temp; | |
141 | __asm__ __volatile__( | |
142 | " mb\n" | |
143 | "1: ldq_l %0,%1\n" | |
144 | " subq %0,%3,%2\n" | |
145 | " stq_c %2,%1\n" | |
146 | " beq %2,2f\n" | |
147 | ".subsection 2\n" | |
148 | "2: br 1b\n" | |
149 | ".previous" | |
150 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
151 | :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory"); | |
152 | #endif | |
153 | if (unlikely(oldcount < 0)) | |
154 | if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0) | |
155 | rwsem_wake(sem); | |
156 | } | |
157 | ||
158 | static inline void __up_write(struct rw_semaphore *sem) | |
159 | { | |
160 | long count; | |
161 | #ifndef CONFIG_SMP | |
162 | sem->count -= RWSEM_ACTIVE_WRITE_BIAS; | |
163 | count = sem->count; | |
164 | #else | |
165 | long temp; | |
166 | __asm__ __volatile__( | |
167 | " mb\n" | |
168 | "1: ldq_l %0,%1\n" | |
169 | " subq %0,%3,%2\n" | |
170 | " stq_c %2,%1\n" | |
171 | " beq %2,2f\n" | |
172 | " subq %0,%3,%0\n" | |
173 | ".subsection 2\n" | |
174 | "2: br 1b\n" | |
175 | ".previous" | |
176 | :"=&r" (count), "=m" (sem->count), "=&r" (temp) | |
177 | :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory"); | |
178 | #endif | |
179 | if (unlikely(count)) | |
180 | if ((int)count == 0) | |
181 | rwsem_wake(sem); | |
182 | } | |
183 | ||
184 | /* | |
185 | * downgrade write lock to read lock | |
186 | */ | |
187 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
188 | { | |
189 | long oldcount; | |
190 | #ifndef CONFIG_SMP | |
191 | oldcount = sem->count; | |
192 | sem->count -= RWSEM_WAITING_BIAS; | |
193 | #else | |
194 | long temp; | |
195 | __asm__ __volatile__( | |
196 | "1: ldq_l %0,%1\n" | |
197 | " addq %0,%3,%2\n" | |
198 | " stq_c %2,%1\n" | |
199 | " beq %2,2f\n" | |
200 | " mb\n" | |
201 | ".subsection 2\n" | |
202 | "2: br 1b\n" | |
203 | ".previous" | |
204 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
205 | :"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory"); | |
206 | #endif | |
207 | if (unlikely(oldcount < 0)) | |
208 | rwsem_downgrade_wake(sem); | |
209 | } | |
210 | ||
211 | static inline void rwsem_atomic_add(long val, struct rw_semaphore *sem) | |
212 | { | |
213 | #ifndef CONFIG_SMP | |
214 | sem->count += val; | |
215 | #else | |
216 | long temp; | |
217 | __asm__ __volatile__( | |
218 | "1: ldq_l %0,%1\n" | |
219 | " addq %0,%2,%0\n" | |
220 | " stq_c %0,%1\n" | |
221 | " beq %0,2f\n" | |
222 | ".subsection 2\n" | |
223 | "2: br 1b\n" | |
224 | ".previous" | |
225 | :"=&r" (temp), "=m" (sem->count) | |
226 | :"Ir" (val), "m" (sem->count)); | |
227 | #endif | |
228 | } | |
229 | ||
230 | static inline long rwsem_atomic_update(long val, struct rw_semaphore *sem) | |
231 | { | |
232 | #ifndef CONFIG_SMP | |
233 | sem->count += val; | |
234 | return sem->count; | |
235 | #else | |
236 | long ret, temp; | |
237 | __asm__ __volatile__( | |
238 | "1: ldq_l %0,%1\n" | |
239 | " addq %0,%3,%2\n" | |
240 | " addq %0,%3,%0\n" | |
241 | " stq_c %2,%1\n" | |
242 | " beq %2,2f\n" | |
243 | ".subsection 2\n" | |
244 | "2: br 1b\n" | |
245 | ".previous" | |
246 | :"=&r" (ret), "=m" (sem->count), "=&r" (temp) | |
247 | :"Ir" (val), "m" (sem->count)); | |
248 | ||
249 | return ret; | |
250 | #endif | |
251 | } | |
252 | ||
eb92f4ef RVR |
253 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
254 | { | |
255 | return (sem->count != 0); | |
256 | } | |
257 | ||
1da177e4 LT |
258 | #endif /* __KERNEL__ */ |
259 | #endif /* _ALPHA_RWSEM_H */ |