Commit | Line | Data |
---|---|---|
e172800e WD |
1 | #ifndef _ASM_GENERIC_RWSEM_H |
2 | #define _ASM_GENERIC_RWSEM_H | |
dd472da3 RK |
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 | /* | |
e172800e | 11 | * R/W semaphores originally for PPC using the stuff in lib/rwsem.c. |
dd472da3 RK |
12 | * Adapted largely from include/asm-i386/rwsem.h |
13 | * by Paul Mackerras <paulus@samba.org>. | |
14 | */ | |
15 | ||
16 | /* | |
17 | * the semaphore definition | |
18 | */ | |
e172800e | 19 | #ifdef CONFIG_64BIT |
dd472da3 RK |
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 | { | |
00eb4bab | 36 | if (unlikely(atomic_long_inc_return_acquire((atomic_long_t *)&sem->count) <= 0)) |
dd472da3 RK |
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) { | |
00eb4bab | 45 | if (tmp == cmpxchg_acquire(&sem->count, tmp, |
dd472da3 RK |
46 | tmp + RWSEM_ACTIVE_READ_BIAS)) { |
47 | return 1; | |
48 | } | |
49 | } | |
50 | return 0; | |
51 | } | |
52 | ||
53 | /* | |
54 | * lock for writing | |
55 | */ | |
f8e04d85 | 56 | static inline void __down_write(struct rw_semaphore *sem) |
dd472da3 RK |
57 | { |
58 | long tmp; | |
59 | ||
00eb4bab | 60 | tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, |
dd472da3 RK |
61 | (atomic_long_t *)&sem->count); |
62 | if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) | |
63 | rwsem_down_write_failed(sem); | |
64 | } | |
65 | ||
dd472da3 RK |
66 | static inline int __down_write_trylock(struct rw_semaphore *sem) |
67 | { | |
68 | long tmp; | |
69 | ||
00eb4bab | 70 | tmp = cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE, |
dd472da3 RK |
71 | RWSEM_ACTIVE_WRITE_BIAS); |
72 | return tmp == RWSEM_UNLOCKED_VALUE; | |
73 | } | |
74 | ||
75 | /* | |
76 | * unlock after reading | |
77 | */ | |
78 | static inline void __up_read(struct rw_semaphore *sem) | |
79 | { | |
80 | long tmp; | |
81 | ||
00eb4bab | 82 | tmp = atomic_long_dec_return_release((atomic_long_t *)&sem->count); |
dd472da3 RK |
83 | if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)) |
84 | rwsem_wake(sem); | |
85 | } | |
86 | ||
87 | /* | |
88 | * unlock after writing | |
89 | */ | |
90 | static inline void __up_write(struct rw_semaphore *sem) | |
91 | { | |
00eb4bab | 92 | if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS, |
dd472da3 RK |
93 | (atomic_long_t *)&sem->count) < 0)) |
94 | rwsem_wake(sem); | |
95 | } | |
96 | ||
97 | /* | |
98 | * implement atomic add functionality | |
99 | */ | |
100 | static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem) | |
101 | { | |
102 | atomic_long_add(delta, (atomic_long_t *)&sem->count); | |
103 | } | |
104 | ||
105 | /* | |
106 | * downgrade write lock to read lock | |
107 | */ | |
108 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
109 | { | |
110 | long tmp; | |
111 | ||
00eb4bab DB |
112 | /* |
113 | * When downgrading from exclusive to shared ownership, | |
114 | * anything inside the write-locked region cannot leak | |
115 | * into the read side. In contrast, anything in the | |
116 | * read-locked region is ok to be re-ordered into the | |
117 | * write side. As such, rely on RELEASE semantics. | |
118 | */ | |
119 | tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, | |
dd472da3 RK |
120 | (atomic_long_t *)&sem->count); |
121 | if (tmp < 0) | |
122 | rwsem_downgrade_wake(sem); | |
123 | } | |
124 | ||
125 | /* | |
126 | * implement exchange and add functionality | |
127 | */ | |
128 | static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem) | |
129 | { | |
130 | return atomic_long_add_return(delta, (atomic_long_t *)&sem->count); | |
131 | } | |
132 | ||
133 | #endif /* __KERNEL__ */ | |
e172800e | 134 | #endif /* _ASM_GENERIC_RWSEM_H */ |