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 /*
17 * the semaphore definition
18 */
19 #ifdef CONFIG_PPC64
20 # define RWSEM_ACTIVE_MASK 0xffffffffL
21 #else
22 # define RWSEM_ACTIVE_MASK 0x0000ffffL
23 #endif
24
25 #define RWSEM_UNLOCKED_VALUE 0x00000000L
26 #define RWSEM_ACTIVE_BIAS 0x00000001L
27 #define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
28 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
29 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
30
31 /*
32 * lock for reading
33 */
__down_read(struct rw_semaphore * sem)34 static inline void __down_read(struct rw_semaphore *sem)
35 {
36 if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
37 rwsem_down_read_failed(sem);
38 }
39
__down_read_trylock(struct rw_semaphore * sem)40 static inline int __down_read_trylock(struct rw_semaphore *sem)
41 {
42 long tmp;
43
44 while ((tmp = sem->count) >= 0) {
45 if (tmp == cmpxchg(&sem->count, tmp,
46 tmp + RWSEM_ACTIVE_READ_BIAS)) {
47 return 1;
48 }
49 }
50 return 0;
51 }
52
53 /*
54 * lock for writing
55 */
__down_write_nested(struct rw_semaphore * sem,int subclass)56 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
57 {
58 long tmp;
59
60 tmp = atomic_long_add_return(RWSEM_ACTIVE_WRITE_BIAS,
61 (atomic_long_t *)&sem->count);
62 if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
63 rwsem_down_write_failed(sem);
64 }
65
__down_write(struct rw_semaphore * sem)66 static inline void __down_write(struct rw_semaphore *sem)
67 {
68 __down_write_nested(sem, 0);
69 }
70
__down_write_trylock(struct rw_semaphore * sem)71 static inline int __down_write_trylock(struct rw_semaphore *sem)
72 {
73 long tmp;
74
75 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
76 RWSEM_ACTIVE_WRITE_BIAS);
77 return tmp == RWSEM_UNLOCKED_VALUE;
78 }
79
80 /*
81 * unlock after reading
82 */
__up_read(struct rw_semaphore * sem)83 static inline void __up_read(struct rw_semaphore *sem)
84 {
85 long tmp;
86
87 tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
88 if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
89 rwsem_wake(sem);
90 }
91
92 /*
93 * unlock after writing
94 */
__up_write(struct rw_semaphore * sem)95 static inline void __up_write(struct rw_semaphore *sem)
96 {
97 if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
98 (atomic_long_t *)&sem->count) < 0))
99 rwsem_wake(sem);
100 }
101
102 /*
103 * implement atomic add functionality
104 */
rwsem_atomic_add(long delta,struct rw_semaphore * sem)105 static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
106 {
107 atomic_long_add(delta, (atomic_long_t *)&sem->count);
108 }
109
110 /*
111 * downgrade write lock to read lock
112 */
__downgrade_write(struct rw_semaphore * sem)113 static inline void __downgrade_write(struct rw_semaphore *sem)
114 {
115 long tmp;
116
117 tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
118 (atomic_long_t *)&sem->count);
119 if (tmp < 0)
120 rwsem_downgrade_wake(sem);
121 }
122
123 /*
124 * implement exchange and add functionality
125 */
rwsem_atomic_update(long delta,struct rw_semaphore * sem)126 static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
127 {
128 return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
129 }
130
131 #endif /* __KERNEL__ */
132 #endif /* _ASM_POWERPC_RWSEM_H */
133