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 */
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 #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
53 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
54 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
55 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
56 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
57
58 extern 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 */
__down_read(struct rw_semaphore * sem)71 static 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
__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 return 1;
85 }
86 }
87 return 0;
88 }
89
90 /*
91 * lock for writing
92 */
__down_write_nested(struct rw_semaphore * sem,int subclass)93 static 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
__down_write(struct rw_semaphore * sem)103 static inline void __down_write(struct rw_semaphore *sem)
104 {
105 __down_write_nested(sem, 0);
106 }
107
__down_write_trylock(struct rw_semaphore * sem)108 static 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 */
__up_read(struct rw_semaphore * sem)120 static 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 */
__up_write(struct rw_semaphore * sem)132 static 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 */
rwsem_atomic_add(int delta,struct rw_semaphore * sem)142 static 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 */
__downgrade_write(struct rw_semaphore * sem)150 static 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 */
rwsem_atomic_update(int delta,struct rw_semaphore * sem)162 static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
163 {
164 return atomic_add_return(delta, (atomic_t *)(&sem->count));
165 }
166
rwsem_is_locked(struct rw_semaphore * sem)167 static 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 */
174