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1 | /* kernel/rwsem.c: R/W semaphores, public implementation |
2 | * |
3 | * Written by David Howells (dhowells@redhat.com). |
4 | * Derived from asm-i386/semaphore.h |
5 | */ |
6 | |
7 | #include <linux/types.h> |
8 | #include <linux/kernel.h> |
9 | #include <linux/sched.h> |
10 | #include <linux/module.h> |
11 | #include <linux/rwsem.h> |
12 | |
13 | #include <asm/system.h> |
14 | #include <asm/atomic.h> |
15 | |
16 | /* |
17 | * lock for reading |
18 | */ |
19 | void __sched down_read(struct rw_semaphore *sem) |
20 | { |
21 | might_sleep(); |
22 | rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); |
23 | |
24 | LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
25 | } |
26 | |
27 | EXPORT_SYMBOL(down_read); |
28 | |
29 | /* |
30 | * trylock for reading -- returns 1 if successful, 0 if contention |
31 | */ |
32 | int down_read_trylock(struct rw_semaphore *sem) |
33 | { |
34 | int ret = __down_read_trylock(sem); |
35 | |
36 | if (ret == 1) |
37 | rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); |
38 | return ret; |
39 | } |
40 | |
41 | EXPORT_SYMBOL(down_read_trylock); |
42 | |
43 | /* |
44 | * lock for writing |
45 | */ |
46 | void __sched down_write(struct rw_semaphore *sem) |
47 | { |
48 | might_sleep(); |
49 | rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); |
50 | |
51 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
52 | } |
53 | |
54 | EXPORT_SYMBOL(down_write); |
55 | |
56 | /* |
57 | * trylock for writing -- returns 1 if successful, 0 if contention |
58 | */ |
59 | int down_write_trylock(struct rw_semaphore *sem) |
60 | { |
61 | int ret = __down_write_trylock(sem); |
62 | |
63 | if (ret == 1) |
64 | rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); |
65 | return ret; |
66 | } |
67 | |
68 | EXPORT_SYMBOL(down_write_trylock); |
69 | |
70 | /* |
71 | * release a read lock |
72 | */ |
73 | void up_read(struct rw_semaphore *sem) |
74 | { |
75 | rwsem_release(&sem->dep_map, 1, _RET_IP_); |
76 | |
77 | __up_read(sem); |
78 | } |
79 | |
80 | EXPORT_SYMBOL(up_read); |
81 | |
82 | /* |
83 | * release a write lock |
84 | */ |
85 | void up_write(struct rw_semaphore *sem) |
86 | { |
87 | rwsem_release(&sem->dep_map, 1, _RET_IP_); |
88 | |
89 | __up_write(sem); |
90 | } |
91 | |
92 | EXPORT_SYMBOL(up_write); |
93 | |
94 | /* |
95 | * downgrade write lock to read lock |
96 | */ |
97 | void downgrade_write(struct rw_semaphore *sem) |
98 | { |
99 | /* |
100 | * lockdep: a downgraded write will live on as a write |
101 | * dependency. |
102 | */ |
103 | __downgrade_write(sem); |
104 | } |
105 | |
106 | EXPORT_SYMBOL(downgrade_write); |
107 | |
108 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
109 | |
110 | void down_read_nested(struct rw_semaphore *sem, int subclass) |
111 | { |
112 | might_sleep(); |
113 | rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); |
114 | |
115 | LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
116 | } |
117 | |
118 | EXPORT_SYMBOL(down_read_nested); |
119 | |
120 | void down_read_non_owner(struct rw_semaphore *sem) |
121 | { |
122 | might_sleep(); |
123 | |
124 | __down_read(sem); |
125 | } |
126 | |
127 | EXPORT_SYMBOL(down_read_non_owner); |
128 | |
129 | void down_write_nested(struct rw_semaphore *sem, int subclass) |
130 | { |
131 | might_sleep(); |
132 | rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); |
133 | |
134 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
135 | } |
136 | |
137 | EXPORT_SYMBOL(down_write_nested); |
138 | |
139 | void up_read_non_owner(struct rw_semaphore *sem) |
140 | { |
141 | __up_read(sem); |
142 | } |
143 | |
144 | EXPORT_SYMBOL(up_read_non_owner); |
145 | |
146 | #endif |
147 | |
148 | |
149 |
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