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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * include/asm-ppc/rwsem.h: R/W semaphores for SH using the stuff
3 * in lib/rwsem.c.
4 */
5
6#ifndef _ASM_SH_RWSEM_H
7#define _ASM_SH_RWSEM_H
8
9#ifdef __KERNEL__
10#include <linux/list.h>
11#include <linux/spinlock.h>
12#include <asm/atomic.h>
13#include <asm/system.h>
14
15/*
16 * the semaphore definition
17 */
18struct rw_semaphore {
19 long count;
20#define RWSEM_UNLOCKED_VALUE 0x00000000
21#define RWSEM_ACTIVE_BIAS 0x00000001
22#define RWSEM_ACTIVE_MASK 0x0000ffff
23#define RWSEM_WAITING_BIAS (-0x00010000)
24#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
25#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
26 spinlock_t wait_lock;
27 struct list_head wait_list;
28#ifdef CONFIG_DEBUG_LOCK_ALLOC
29 struct lockdep_map dep_map;
30#endif
31};
32
33#ifdef CONFIG_DEBUG_LOCK_ALLOC
34# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
35#else
36# define __RWSEM_DEP_MAP_INIT(lockname)
37#endif
38
39#define __RWSEM_INITIALIZER(name) \
40 { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
41 LIST_HEAD_INIT((name).wait_list) \
42 __RWSEM_DEP_MAP_INIT(name) }
43
44#define DECLARE_RWSEM(name) \
45 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
46
47extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
48extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
49extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
50extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
51
52extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
53 struct lock_class_key *key);
54
55#define init_rwsem(sem) \
56do { \
57 static struct lock_class_key __key; \
58 \
59 __init_rwsem((sem), #sem, &__key); \
60} while (0)
61
62static inline void init_rwsem(struct rw_semaphore *sem)
63{
64 sem->count = RWSEM_UNLOCKED_VALUE;
65 spin_lock_init(&sem->wait_lock);
66 INIT_LIST_HEAD(&sem->wait_list);
67}
68
69/*
70 * lock for reading
71 */
72static inline void __down_read(struct rw_semaphore *sem)
73{
74 if (atomic_inc_return((atomic_t *)(&sem->count)) > 0)
75 smp_wmb();
76 else
77 rwsem_down_read_failed(sem);
78}
79
80static inline int __down_read_trylock(struct rw_semaphore *sem)
81{
82 int tmp;
83
84 while ((tmp = sem->count) >= 0) {
85 if (tmp == cmpxchg(&sem->count, tmp,
86 tmp + RWSEM_ACTIVE_READ_BIAS)) {
87 smp_wmb();
88 return 1;
89 }
90 }
91 return 0;
92}
93
94/*
95 * lock for writing
96 */
97static inline void __down_write(struct rw_semaphore *sem)
98{
99 int tmp;
100
101 tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
102 (atomic_t *)(&sem->count));
103 if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
104 smp_wmb();
105 else
106 rwsem_down_write_failed(sem);
107}
108
109static inline int __down_write_trylock(struct rw_semaphore *sem)
110{
111 int tmp;
112
113 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
114 RWSEM_ACTIVE_WRITE_BIAS);
115 smp_wmb();
116 return tmp == RWSEM_UNLOCKED_VALUE;
117}
118
119/*
120 * unlock after reading
121 */
122static inline void __up_read(struct rw_semaphore *sem)
123{
124 int tmp;
125
126 smp_wmb();
127 tmp = atomic_dec_return((atomic_t *)(&sem->count));
128 if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
129 rwsem_wake(sem);
130}
131
132/*
133 * unlock after writing
134 */
135static inline void __up_write(struct rw_semaphore *sem)
136{
137 smp_wmb();
138 if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
139 (atomic_t *)(&sem->count)) < 0)
140 rwsem_wake(sem);
141}
142
143/*
144 * implement atomic add functionality
145 */
146static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
147{
148 atomic_add(delta, (atomic_t *)(&sem->count));
149}
150
151/*
152 * downgrade write lock to read lock
153 */
154static inline void __downgrade_write(struct rw_semaphore *sem)
155{
156 int tmp;
157
158 smp_wmb();
159 tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
160 if (tmp < 0)
161 rwsem_downgrade_wake(sem);
162}
163
164static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
165{
166 __down_write(sem);
167}
168
169/*
170 * implement exchange and add functionality
171 */
172static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
173{
174 smp_mb();
175 return atomic_add_return(delta, (atomic_t *)(&sem->count));
176}
177
178static inline int rwsem_is_locked(struct rw_semaphore *sem)
179{
180 return (sem->count != 0);
181}
182
183#endif /* __KERNEL__ */
184#endif /* _ASM_SH_RWSEM_H */