tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
fork
Configure Feed
Select the types of activity you want to include in your feed.
1#ifndef _ASM_POWERPC_RWSEM_H
2#define _ASM_POWERPC_RWSEM_H
3
4#ifndef _LINUX_RWSEM_H
5#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
6#endif
7
8#ifdef __KERNEL__
9
10/*
11 * R/W semaphores for PPC using the stuff in lib/rwsem.c.
12 * Adapted largely from include/asm-i386/rwsem.h
13 * by Paul Mackerras <paulus@samba.org>.
14 */
15
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 */
24struct 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#ifdef CONFIG_DEBUG_LOCK_ALLOC
36 struct lockdep_map dep_map;
37#endif
38};
39
40#ifdef CONFIG_DEBUG_LOCK_ALLOC
41# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
42#else
43# define __RWSEM_DEP_MAP_INIT(lockname)
44#endif
45
46#define __RWSEM_INITIALIZER(name) \
47 { RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
48 LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
49
50#define DECLARE_RWSEM(name) \
51 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
52
53extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
54extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
55extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
56extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
57
58extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
59 struct lock_class_key *key);
60
61#define init_rwsem(sem) \
62 do { \
63 static struct lock_class_key __key; \
64 \
65 __init_rwsem((sem), #sem, &__key); \
66 } while (0)
67
68/*
69 * lock for reading
70 */
71static 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
77static 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 */
93static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
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
103static inline void __down_write(struct rw_semaphore *sem)
104{
105 __down_write_nested(sem, 0);
106}
107
108static inline int __down_write_trylock(struct rw_semaphore *sem)
109{
110 int tmp;
111
112 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
113 RWSEM_ACTIVE_WRITE_BIAS);
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 tmp = atomic_dec_return((atomic_t *)(&sem->count));
125 if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
126 rwsem_wake(sem);
127}
128
129/*
130 * unlock after writing
131 */
132static inline void __up_write(struct rw_semaphore *sem)
133{
134 if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
135 (atomic_t *)(&sem->count)) < 0))
136 rwsem_wake(sem);
137}
138
139/*
140 * implement atomic add functionality
141 */
142static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
143{
144 atomic_add(delta, (atomic_t *)(&sem->count));
145}
146
147/*
148 * downgrade write lock to read lock
149 */
150static inline void __downgrade_write(struct rw_semaphore *sem)
151{
152 int tmp;
153
154 tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
155 if (tmp < 0)
156 rwsem_downgrade_wake(sem);
157}
158
159/*
160 * implement exchange and add functionality
161 */
162static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
163{
164 return atomic_add_return(delta, (atomic_t *)(&sem->count));
165}
166
167static inline int rwsem_is_locked(struct rw_semaphore *sem)
168{
169 return (sem->count != 0);
170}
171
172#endif /* __KERNEL__ */
173#endif /* _ASM_POWERPC_RWSEM_H */