Merge branches 'devel-stable', 'entry', 'fixes', 'mach-types', 'misc' and 'smp-hotplu...
[linux-3.10.git] / include / asm-generic / rwsem.h
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  */
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
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  */
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
66 static inline void __down_write(struct rw_semaphore *sem)
67 {
68         __down_write_nested(sem, 0);
69 }
70
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  */
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  */
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  */
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  */
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  */
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 */