[PATCH] add sem_is_read/write_locked()
[linux-2.6.git] / include / asm-alpha / rwsem.h
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 static inline int rwsem_is_locked(struct rw_semaphore *sem)
266 {
267         return (sem->count != 0);
268 }
269
270 #endif /* __KERNEL__ */
271 #endif /* _ALPHA_RWSEM_H */