[PATCH] powerpc: Merge asm-ppc*/rwsem.h
[linux-2.6.git] / include / asm-powerpc / rwsem.h
1 #ifndef _ASM_POWERPC_RWSEM_H
2 #define _ASM_POWERPC_RWSEM_H
3
4 #ifdef __KERNEL__
5
6 /*
7  * include/asm-ppc64/rwsem.h: R/W semaphores for PPC using the stuff
8  * in lib/rwsem.c.  Adapted largely from include/asm-i386/rwsem.h
9  * by Paul Mackerras <paulus@samba.org>.
10  */
11
12 #include <linux/list.h>
13 #include <linux/spinlock.h>
14 #include <asm/atomic.h>
15 #include <asm/system.h>
16
17 /*
18  * the semaphore definition
19  */
20 struct rw_semaphore {
21         /* XXX this should be able to be an atomic_t  -- paulus */
22         signed int              count;
23 #define RWSEM_UNLOCKED_VALUE            0x00000000
24 #define RWSEM_ACTIVE_BIAS               0x00000001
25 #define RWSEM_ACTIVE_MASK               0x0000ffff
26 #define RWSEM_WAITING_BIAS              (-0x00010000)
27 #define RWSEM_ACTIVE_READ_BIAS          RWSEM_ACTIVE_BIAS
28 #define RWSEM_ACTIVE_WRITE_BIAS         (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
29         spinlock_t              wait_lock;
30         struct list_head        wait_list;
31 #if RWSEM_DEBUG
32         int                     debug;
33 #endif
34 };
35
36 /*
37  * initialisation
38  */
39 #if RWSEM_DEBUG
40 #define __RWSEM_DEBUG_INIT      , 0
41 #else
42 #define __RWSEM_DEBUG_INIT      /* */
43 #endif
44
45 #define __RWSEM_INITIALIZER(name) \
46         { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
47           LIST_HEAD_INIT((name).wait_list) \
48           __RWSEM_DEBUG_INIT }
49
50 #define DECLARE_RWSEM(name)             \
51         struct rw_semaphore name = __RWSEM_INITIALIZER(name)
52
53 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
54 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
55 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
56 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
57
58 static inline void init_rwsem(struct rw_semaphore *sem)
59 {
60         sem->count = RWSEM_UNLOCKED_VALUE;
61         spin_lock_init(&sem->wait_lock);
62         INIT_LIST_HEAD(&sem->wait_list);
63 #if RWSEM_DEBUG
64         sem->debug = 0;
65 #endif
66 }
67
68 /*
69  * lock for reading
70  */
71 static inline void __down_read(struct rw_semaphore *sem)
72 {
73         if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
74                 rwsem_down_read_failed(sem);
75 }
76
77 static inline int __down_read_trylock(struct rw_semaphore *sem)
78 {
79         int tmp;
80
81         while ((tmp = sem->count) >= 0) {
82                 if (tmp == cmpxchg(&sem->count, tmp,
83                                    tmp + RWSEM_ACTIVE_READ_BIAS)) {
84                         return 1;
85                 }
86         }
87         return 0;
88 }
89
90 /*
91  * lock for writing
92  */
93 static inline void __down_write(struct rw_semaphore *sem)
94 {
95         int tmp;
96
97         tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
98                                 (atomic_t *)(&sem->count));
99         if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
100                 rwsem_down_write_failed(sem);
101 }
102
103 static inline int __down_write_trylock(struct rw_semaphore *sem)
104 {
105         int tmp;
106
107         tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
108                       RWSEM_ACTIVE_WRITE_BIAS);
109         return tmp == RWSEM_UNLOCKED_VALUE;
110 }
111
112 /*
113  * unlock after reading
114  */
115 static inline void __up_read(struct rw_semaphore *sem)
116 {
117         int tmp;
118
119         tmp = atomic_dec_return((atomic_t *)(&sem->count));
120         if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
121                 rwsem_wake(sem);
122 }
123
124 /*
125  * unlock after writing
126  */
127 static inline void __up_write(struct rw_semaphore *sem)
128 {
129         if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
130                               (atomic_t *)(&sem->count)) < 0))
131                 rwsem_wake(sem);
132 }
133
134 /*
135  * implement atomic add functionality
136  */
137 static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
138 {
139         atomic_add(delta, (atomic_t *)(&sem->count));
140 }
141
142 /*
143  * downgrade write lock to read lock
144  */
145 static inline void __downgrade_write(struct rw_semaphore *sem)
146 {
147         int tmp;
148
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         return atomic_add_return(delta, (atomic_t *)(&sem->count));
160 }
161
162 #endif  /* __KERNEL__ */
163 #endif  /* _ASM_POWERPC_RWSEM_H */