1 /*
2 * include/asm-ppc/rwsem.h: R/W semaphores for PPC using the stuff
3 * in lib/rwsem.c. Adapted largely from include/asm-i386/rwsem.h
4 * by Paul Mackerras <paulus@samba.org>.
5 */
6
7 #ifndef _PPC_RWSEM_H
8 #define _PPC_RWSEM_H
9
10 #ifdef __KERNEL__
11 #include <linux/list.h>
12 #include <linux/spinlock.h>
13 #include <asm/atomic.h>
14 #include <asm/system.h>
15
16 /*
17 * the semaphore definition
18 */
19 struct rw_semaphore {
20 /* XXX this should be able to be an atomic_t -- paulus */
21 signed long count;
22 #define RWSEM_UNLOCKED_VALUE 0x00000000
23 #define RWSEM_ACTIVE_BIAS 0x00000001
24 #define RWSEM_ACTIVE_MASK 0x0000ffff
25 #define RWSEM_WAITING_BIAS (-0x00010000)
26 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
27 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
28 spinlock_t wait_lock;
29 struct list_head wait_list;
30 #if RWSEM_DEBUG
31 int debug;
32 #endif
33 };
34
35 /*
36 * initialisation
37 */
38 #if RWSEM_DEBUG
39 #define __RWSEM_DEBUG_INIT , 0
40 #else
41 #define __RWSEM_DEBUG_INIT /* */
42 #endif
43
44 #define __RWSEM_INITIALIZER(name) \
45 { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
46 LIST_HEAD_INIT((name).wait_list) \
47 __RWSEM_DEBUG_INIT }
48
49 #define DECLARE_RWSEM(name) \
50 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
51
52 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
53 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
54 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
55
init_rwsem(struct rw_semaphore * sem)56 static inline void init_rwsem(struct rw_semaphore *sem)
57 {
58 sem->count = RWSEM_UNLOCKED_VALUE;
59 spin_lock_init(&sem->wait_lock);
60 INIT_LIST_HEAD(&sem->wait_list);
61 #if RWSEM_DEBUG
62 sem->debug = 0;
63 #endif
64 }
65
66 /*
67 * lock for reading
68 */
__down_read(struct rw_semaphore * sem)69 static inline void __down_read(struct rw_semaphore *sem)
70 {
71 if (atomic_inc_return((atomic_t *)(&sem->count)) >= 0)
72 smp_wmb();
73 else
74 rwsem_down_read_failed(sem);
75 }
76
__down_read_trylock(struct rw_semaphore * sem)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 smp_wmb();
85 return 1;
86 }
87 }
88 return 0;
89 }
90
91 /*
92 * lock for writing
93 */
__down_write(struct rw_semaphore * sem)94 static inline void __down_write(struct rw_semaphore *sem)
95 {
96 int tmp;
97
98 tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
99 (atomic_t *)(&sem->count));
100 if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
101 smp_wmb();
102 else
103 rwsem_down_write_failed(sem);
104 }
105
__down_write_trylock(struct rw_semaphore * sem)106 static inline int __down_write_trylock(struct rw_semaphore *sem)
107 {
108 int tmp;
109
110 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
111 RWSEM_ACTIVE_WRITE_BIAS);
112 smp_wmb();
113 return tmp == RWSEM_UNLOCKED_VALUE;
114 }
115
116 /*
117 * unlock after reading
118 */
__up_read(struct rw_semaphore * sem)119 static inline void __up_read(struct rw_semaphore *sem)
120 {
121 int tmp;
122
123 smp_wmb();
124 tmp = atomic_dec_return((atomic_t *)(&sem->count));
125 if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
126 rwsem_wake(sem);
127 }
128
129 /*
130 * unlock after writing
131 */
__up_write(struct rw_semaphore * sem)132 static inline void __up_write(struct rw_semaphore *sem)
133 {
134 smp_wmb();
135 if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
136 (atomic_t *)(&sem->count)) < 0)
137 rwsem_wake(sem);
138 }
139
140 /*
141 * implement atomic add functionality
142 */
rwsem_atomic_add(int delta,struct rw_semaphore * sem)143 static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
144 {
145 atomic_add(delta, (atomic_t *)(&sem->count));
146 }
147
148 /*
149 * implement exchange and add functionality
150 */
rwsem_atomic_update(int delta,struct rw_semaphore * sem)151 static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
152 {
153 smp_mb();
154 return atomic_add_return(delta, (atomic_t *)(&sem->count));
155 }
156
157 #endif /* __KERNEL__ */
158 #endif /* _PPC_RWSEM_XADD_H */
159