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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 |
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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 | { | |
06321dd2 | 36 | if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) |
dd472da3 RK |
37 | rwsem_down_read_failed(sem); |
38 | } | |
39 | ||
76f8507f KT |
40 | static inline int __down_read_killable(struct rw_semaphore *sem) |
41 | { | |
42 | if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) { | |
43 | if (IS_ERR(rwsem_down_read_failed_killable(sem))) | |
44 | return -EINTR; | |
45 | } | |
46 | ||
47 | return 0; | |
48 | } | |
49 | ||
dd472da3 RK |
50 | static inline int __down_read_trylock(struct rw_semaphore *sem) |
51 | { | |
52 | long tmp; | |
53 | ||
8ee62b18 JL |
54 | while ((tmp = atomic_long_read(&sem->count)) >= 0) { |
55 | if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, | |
dd472da3 RK |
56 | tmp + RWSEM_ACTIVE_READ_BIAS)) { |
57 | return 1; | |
58 | } | |
59 | } | |
60 | return 0; | |
61 | } | |
62 | ||
63 | /* | |
64 | * lock for writing | |
65 | */ | |
f8e04d85 | 66 | static inline void __down_write(struct rw_semaphore *sem) |
dd472da3 RK |
67 | { |
68 | long tmp; | |
69 | ||
00eb4bab | 70 | tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, |
06321dd2 | 71 | &sem->count); |
dd472da3 RK |
72 | if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) |
73 | rwsem_down_write_failed(sem); | |
74 | } | |
75 | ||
d4799608 MH |
76 | static inline int __down_write_killable(struct rw_semaphore *sem) |
77 | { | |
78 | long tmp; | |
79 | ||
80 | tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, | |
06321dd2 | 81 | &sem->count); |
d4799608 MH |
82 | if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) |
83 | if (IS_ERR(rwsem_down_write_failed_killable(sem))) | |
84 | return -EINTR; | |
85 | return 0; | |
86 | } | |
87 | ||
dd472da3 RK |
88 | static inline int __down_write_trylock(struct rw_semaphore *sem) |
89 | { | |
90 | long tmp; | |
91 | ||
8ee62b18 | 92 | tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE, |
dd472da3 RK |
93 | RWSEM_ACTIVE_WRITE_BIAS); |
94 | return tmp == RWSEM_UNLOCKED_VALUE; | |
95 | } | |
96 | ||
97 | /* | |
98 | * unlock after reading | |
99 | */ | |
100 | static inline void __up_read(struct rw_semaphore *sem) | |
101 | { | |
102 | long tmp; | |
103 | ||
06321dd2 | 104 | tmp = atomic_long_dec_return_release(&sem->count); |
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105 | if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)) |
106 | rwsem_wake(sem); | |
107 | } | |
108 | ||
109 | /* | |
110 | * unlock after writing | |
111 | */ | |
112 | static inline void __up_write(struct rw_semaphore *sem) | |
113 | { | |
00eb4bab | 114 | if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS, |
06321dd2 | 115 | &sem->count) < 0)) |
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116 | rwsem_wake(sem); |
117 | } | |
118 | ||
dd472da3 RK |
119 | /* |
120 | * downgrade write lock to read lock | |
121 | */ | |
122 | static inline void __downgrade_write(struct rw_semaphore *sem) | |
123 | { | |
124 | long tmp; | |
125 | ||
00eb4bab DB |
126 | /* |
127 | * When downgrading from exclusive to shared ownership, | |
128 | * anything inside the write-locked region cannot leak | |
129 | * into the read side. In contrast, anything in the | |
130 | * read-locked region is ok to be re-ordered into the | |
131 | * write side. As such, rely on RELEASE semantics. | |
132 | */ | |
06321dd2 | 133 | tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, &sem->count); |
dd472da3 RK |
134 | if (tmp < 0) |
135 | rwsem_downgrade_wake(sem); | |
136 | } | |
137 | ||
dd472da3 | 138 | #endif /* __KERNEL__ */ |
e172800e | 139 | #endif /* _ASM_GENERIC_RWSEM_H */ |