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gerrit-public.fairphone.software / kernel / msm-4.9 / 3f3ae3471f4c5921274c3869eef21b5611e85b50 / . / include / asm-ppc / rwsem.h
blob: 3e738f483c11b1e2ccc745ec7527f5d3ee94a375 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]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 */
19struct 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
52extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
53extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
54extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
55extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
56
57static 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/*
68 * lock for reading
69 */
70static inline void __down_read(struct rw_semaphore *sem)
71{
72 if (atomic_inc_return((atomic_t *)(&sem->count)) > 0)
73 smp_wmb();
74 else
75 rwsem_down_read_failed(sem);
76}
77
78static inline int __down_read_trylock(struct rw_semaphore *sem)
79{
80 int tmp;
81
82 while ((tmp = sem->count) >= 0) {
83 if (tmp == cmpxchg(&sem->count, tmp,
84 tmp + RWSEM_ACTIVE_READ_BIAS)) {
85 smp_wmb();
86 return 1;
87 }
88 }
89 return 0;
90}
91
92/*
93 * lock for writing
94 */
95static inline void __down_write(struct rw_semaphore *sem)
96{
97 int tmp;
98
99 tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
100 (atomic_t *)(&sem->count));
101 if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
102 smp_wmb();
103 else
104 rwsem_down_write_failed(sem);
105}
106
107static inline int __down_write_trylock(struct rw_semaphore *sem)
108{
109 int tmp;
110
111 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
112 RWSEM_ACTIVE_WRITE_BIAS);
113 smp_wmb();
114 return tmp == RWSEM_UNLOCKED_VALUE;
115}
116
117/*
118 * unlock after reading
119 */
120static inline void __up_read(struct rw_semaphore *sem)
121{
122 int tmp;
123
124 smp_wmb();
125 tmp = atomic_dec_return((atomic_t *)(&sem->count));
126 if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
127 rwsem_wake(sem);
128}
129
130/*
131 * unlock after writing
132 */
133static inline void __up_write(struct rw_semaphore *sem)
134{
135 smp_wmb();
136 if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
137 (atomic_t *)(&sem->count)) < 0)
138 rwsem_wake(sem);
139}
140
141/*
142 * implement atomic add functionality
143 */
144static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
145{
146 atomic_add(delta, (atomic_t *)(&sem->count));
147}
148
149/*
150 * downgrade write lock to read lock
151 */
152static inline void __downgrade_write(struct rw_semaphore *sem)
153{
154 int tmp;
155
156 smp_wmb();
157 tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
158 if (tmp < 0)
159 rwsem_downgrade_wake(sem);
160}
161
162/*
163 * implement exchange and add functionality
164 */
165static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
166{
167 smp_mb();
168 return atomic_add_return(delta, (atomic_t *)(&sem->count));
169}
170
171#endif /* __KERNEL__ */
172#endif /* _PPC_RWSEM_XADD_H */