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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; | |
39 | #if RWSEM_DEBUG | |
40 | int debug; | |
41 | #endif | |
42 | }; | |
43 | ||
44 | #if RWSEM_DEBUG | |
45 | #define __RWSEM_DEBUG_INIT , 0 | |
46 | #else | |
47 | #define __RWSEM_DEBUG_INIT /* */ | |
48 | #endif | |
49 | ||
50 | #define __RWSEM_INITIALIZER(name) \ | |
51 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
52 | LIST_HEAD_INIT((name).wait_list) __RWSEM_DEBUG_INIT } | |
53 | ||
54 | #define DECLARE_RWSEM(name) \ | |
55 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
56 | ||
57 | static inline void init_rwsem(struct rw_semaphore *sem) | |
58 | { | |
59 | sem->count = RWSEM_UNLOCKED_VALUE; | |
60 | spin_lock_init(&sem->wait_lock); | |
61 | INIT_LIST_HEAD(&sem->wait_list); | |
62 | #if RWSEM_DEBUG | |
63 | sem->debug = 0; | |
64 | #endif | |
65 | } | |
66 | ||
67 | static inline void __down_read(struct rw_semaphore *sem) | |
68 | { | |
69 | long oldcount; | |
70 | #ifndef CONFIG_SMP | |
71 | oldcount = sem->count; | |
72 | sem->count += RWSEM_ACTIVE_READ_BIAS; | |
73 | #else | |
74 | long temp; | |
75 | __asm__ __volatile__( | |
76 | "1: ldq_l %0,%1\n" | |
77 | " addq %0,%3,%2\n" | |
78 | " stq_c %2,%1\n" | |
79 | " beq %2,2f\n" | |
80 | " mb\n" | |
81 | ".subsection 2\n" | |
82 | "2: br 1b\n" | |
83 | ".previous" | |
84 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
85 | :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory"); | |
86 | #endif | |
87 | if (unlikely(oldcount < 0)) | |
88 | rwsem_down_read_failed(sem); | |
89 | } | |
90 | ||
91 | /* | |
92 | * trylock for reading -- returns 1 if successful, 0 if contention | |
93 | */ | |
94 | static inline int __down_read_trylock(struct rw_semaphore *sem) | |
95 | { | |
96 | long old, new, res; | |
97 | ||
98 | res = sem->count; | |
99 | do { | |
100 | new = res + RWSEM_ACTIVE_READ_BIAS; | |
101 | if (new <= 0) | |
102 | break; | |
103 | old = res; | |
104 | res = cmpxchg(&sem->count, old, new); | |
105 | } while (res != old); | |
106 | return res >= 0 ? 1 : 0; | |
107 | } | |
108 | ||
109 | static inline void __down_write(struct rw_semaphore *sem) | |
110 | { | |
111 | long oldcount; | |
112 | #ifndef CONFIG_SMP | |
113 | oldcount = sem->count; | |
114 | sem->count += RWSEM_ACTIVE_WRITE_BIAS; | |
115 | #else | |
116 | long temp; | |
117 | __asm__ __volatile__( | |
118 | "1: ldq_l %0,%1\n" | |
119 | " addq %0,%3,%2\n" | |
120 | " stq_c %2,%1\n" | |
121 | " beq %2,2f\n" | |
122 | " mb\n" | |
123 | ".subsection 2\n" | |
124 | "2: br 1b\n" | |
125 | ".previous" | |
126 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
127 | :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory"); | |
128 | #endif | |
129 | if (unlikely(oldcount)) | |
130 | rwsem_down_write_failed(sem); | |
131 | } | |
132 | ||
133 | /* | |
134 | * trylock for writing -- returns 1 if successful, 0 if contention | |
135 | */ | |
136 | static inline int __down_write_trylock(struct rw_semaphore *sem) | |
137 | { | |
138 | long ret = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, | |
139 | RWSEM_ACTIVE_WRITE_BIAS); | |
140 | if (ret == RWSEM_UNLOCKED_VALUE) | |
141 | return 1; | |
142 | return 0; | |
143 | } | |
144 | ||
145 | static inline void __up_read(struct rw_semaphore *sem) | |
146 | { | |
147 | long oldcount; | |
148 | #ifndef CONFIG_SMP | |
149 | oldcount = sem->count; | |
150 | sem->count -= RWSEM_ACTIVE_READ_BIAS; | |
151 | #else | |
152 | long temp; | |
153 | __asm__ __volatile__( | |
154 | " mb\n" | |
155 | "1: ldq_l %0,%1\n" | |
156 | " subq %0,%3,%2\n" | |
157 | " stq_c %2,%1\n" | |
158 | " beq %2,2f\n" | |
159 | ".subsection 2\n" | |
160 | "2: br 1b\n" | |
161 | ".previous" | |
162 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
163 | :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory"); | |
164 | #endif | |
165 | if (unlikely(oldcount < 0)) | |
166 | if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0) | |
167 | rwsem_wake(sem); | |
168 | } | |
169 | ||
170 | static inline void __up_write(struct rw_semaphore *sem) | |
171 | { | |
172 | long count; | |
173 | #ifndef CONFIG_SMP | |
174 | sem->count -= RWSEM_ACTIVE_WRITE_BIAS; | |
175 | count = sem->count; | |
176 | #else | |
177 | long temp; | |
178 | __asm__ __volatile__( | |
179 | " mb\n" | |
180 | "1: ldq_l %0,%1\n" | |
181 | " subq %0,%3,%2\n" | |
182 | " stq_c %2,%1\n" | |
183 | " beq %2,2f\n" | |
184 | " subq %0,%3,%0\n" | |
185 | ".subsection 2\n" | |
186 | "2: br 1b\n" | |
187 | ".previous" | |
188 | :"=&r" (count), "=m" (sem->count), "=&r" (temp) | |
189 | :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory"); | |
190 | #endif | |
191 | if (unlikely(count)) | |
192 | if ((int)count == 0) | |
193 | rwsem_wake(sem); | |
194 | } | |
195 | ||
196 | /* | |
197 | * downgrade write lock to read lock | |
198 | */ | |
199 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
200 | { | |
201 | long oldcount; | |
202 | #ifndef CONFIG_SMP | |
203 | oldcount = sem->count; | |
204 | sem->count -= RWSEM_WAITING_BIAS; | |
205 | #else | |
206 | long temp; | |
207 | __asm__ __volatile__( | |
208 | "1: ldq_l %0,%1\n" | |
209 | " addq %0,%3,%2\n" | |
210 | " stq_c %2,%1\n" | |
211 | " beq %2,2f\n" | |
212 | " mb\n" | |
213 | ".subsection 2\n" | |
214 | "2: br 1b\n" | |
215 | ".previous" | |
216 | :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp) | |
217 | :"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory"); | |
218 | #endif | |
219 | if (unlikely(oldcount < 0)) | |
220 | rwsem_downgrade_wake(sem); | |
221 | } | |
222 | ||
223 | static inline void rwsem_atomic_add(long val, struct rw_semaphore *sem) | |
224 | { | |
225 | #ifndef CONFIG_SMP | |
226 | sem->count += val; | |
227 | #else | |
228 | long temp; | |
229 | __asm__ __volatile__( | |
230 | "1: ldq_l %0,%1\n" | |
231 | " addq %0,%2,%0\n" | |
232 | " stq_c %0,%1\n" | |
233 | " beq %0,2f\n" | |
234 | ".subsection 2\n" | |
235 | "2: br 1b\n" | |
236 | ".previous" | |
237 | :"=&r" (temp), "=m" (sem->count) | |
238 | :"Ir" (val), "m" (sem->count)); | |
239 | #endif | |
240 | } | |
241 | ||
242 | static inline long rwsem_atomic_update(long val, struct rw_semaphore *sem) | |
243 | { | |
244 | #ifndef CONFIG_SMP | |
245 | sem->count += val; | |
246 | return sem->count; | |
247 | #else | |
248 | long ret, temp; | |
249 | __asm__ __volatile__( | |
250 | "1: ldq_l %0,%1\n" | |
251 | " addq %0,%3,%2\n" | |
252 | " addq %0,%3,%0\n" | |
253 | " stq_c %2,%1\n" | |
254 | " beq %2,2f\n" | |
255 | ".subsection 2\n" | |
256 | "2: br 1b\n" | |
257 | ".previous" | |
258 | :"=&r" (ret), "=m" (sem->count), "=&r" (temp) | |
259 | :"Ir" (val), "m" (sem->count)); | |
260 | ||
261 | return ret; | |
262 | #endif | |
263 | } | |
264 | ||
265 | #endif /* __KERNEL__ */ | |
266 | #endif /* _ALPHA_RWSEM_H */ |