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 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12 #ifndef _PPC64_RWSEM_H
13 #define _PPC64_RWSEM_H
14
15 #ifdef __KERNEL__
16 #include <linux/list.h>
17 #include <linux/spinlock.h>
18 #include <asm/atomic.h>
19 #include <asm/system.h>
20
21 /*
22 * the semaphore definition
23 */
24 struct rw_semaphore {
25 /* XXX this should be able to be an atomic_t -- paulus */
26 signed int count;
27 #define RWSEM_UNLOCKED_VALUE 0x00000000
28 #define RWSEM_ACTIVE_BIAS 0x00000001
29 #define RWSEM_ACTIVE_MASK 0x0000ffff
30 #define RWSEM_WAITING_BIAS (-0x00010000)
31 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
32 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
33 spinlock_t wait_lock;
34 struct list_head wait_list;
35 #if RWSEM_DEBUG
36 int debug;
37 #endif
38 };
39
40 /*
41 * initialisation
42 */
43 #if RWSEM_DEBUG
44 #define __RWSEM_DEBUG_INIT , 0
45 #else
46 #define __RWSEM_DEBUG_INIT /* */
47 #endif
48
49 #define __RWSEM_INITIALIZER(name) \
50 { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
51 LIST_HEAD_INIT((name).wait_list) \
52 __RWSEM_DEBUG_INIT }
53
54 #define DECLARE_RWSEM(name) \
55 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
56
57 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
58 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
59 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
60
init_rwsem(struct rw_semaphore * sem)61 static inline void init_rwsem(struct rw_semaphore *sem)
62 {
63 sem->count = RWSEM_UNLOCKED_VALUE;
64 spin_lock_init(&sem->wait_lock);
65 INIT_LIST_HEAD(&sem->wait_list);
66 #if RWSEM_DEBUG
67 sem->debug = 0;
68 #endif
69 }
70
71 /*
72 * lock for reading
73 */
__down_read(struct rw_semaphore * sem)74 static inline void __down_read(struct rw_semaphore *sem)
75 {
76 if (atomic_inc_return((atomic_t *)(&sem->count)) >= 0)
77 smp_wmb();
78 else
79 rwsem_down_read_failed(sem);
80 }
81
__down_read_trylock(struct rw_semaphore * sem)82 static inline int __down_read_trylock(struct rw_semaphore *sem)
83 {
84 int tmp;
85
86 while ((tmp = sem->count) >= 0) {
87 if (tmp == cmpxchg(&sem->count, tmp,
88 tmp + RWSEM_ACTIVE_READ_BIAS)) {
89 smp_wmb();
90 return 1;
91 }
92 }
93 return 0;
94 }
95
96 /*
97 * lock for writing
98 */
__down_write(struct rw_semaphore * sem)99 static inline void __down_write(struct rw_semaphore *sem)
100 {
101 int tmp;
102
103 tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
104 (atomic_t *)(&sem->count));
105 if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
106 smp_wmb();
107 else
108 rwsem_down_write_failed(sem);
109 }
110
__down_write_trylock(struct rw_semaphore * sem)111 static inline int __down_write_trylock(struct rw_semaphore *sem)
112 {
113 int tmp;
114
115 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
116 RWSEM_ACTIVE_WRITE_BIAS);
117 smp_wmb();
118 return tmp == RWSEM_UNLOCKED_VALUE;
119 }
120
121 /*
122 * unlock after reading
123 */
__up_read(struct rw_semaphore * sem)124 static inline void __up_read(struct rw_semaphore *sem)
125 {
126 int tmp;
127
128 smp_wmb();
129 tmp = atomic_dec_return((atomic_t *)(&sem->count));
130 if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
131 rwsem_wake(sem);
132 }
133
134 /*
135 * unlock after writing
136 */
__up_write(struct rw_semaphore * sem)137 static inline void __up_write(struct rw_semaphore *sem)
138 {
139 smp_wmb();
140 if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
141 (atomic_t *)(&sem->count)) < 0)
142 rwsem_wake(sem);
143 }
144
145 /*
146 * implement atomic add functionality
147 */
rwsem_atomic_add(int delta,struct rw_semaphore * sem)148 static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
149 {
150 atomic_add(delta, (atomic_t *)(&sem->count));
151 }
152
153 /*
154 * implement exchange and add functionality
155 */
rwsem_atomic_update(int delta,struct rw_semaphore * sem)156 static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
157 {
158 smp_mb();
159 return atomic_add_return(delta, (atomic_t *)(&sem->count));
160 }
161
162 #endif /* __KERNEL__ */
163 #endif /* _PPC_RWSEM_XADD_H */
164