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c4e05116 IM |
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> | |
c7af77b5 | 9 | #include <linux/sched.h> |
9984de1a | 10 | #include <linux/export.h> |
c4e05116 IM |
11 | #include <linux/rwsem.h> |
12 | ||
60063497 | 13 | #include <linux/atomic.h> |
c4e05116 | 14 | |
5db6c6fe | 15 | #ifdef CONFIG_RWSEM_SPIN_ON_OWNER |
4fc828e2 DB |
16 | static inline void rwsem_set_owner(struct rw_semaphore *sem) |
17 | { | |
18 | sem->owner = current; | |
19 | } | |
20 | ||
21 | static inline void rwsem_clear_owner(struct rw_semaphore *sem) | |
22 | { | |
23 | sem->owner = NULL; | |
24 | } | |
25 | ||
26 | #else | |
27 | static inline void rwsem_set_owner(struct rw_semaphore *sem) | |
28 | { | |
29 | } | |
30 | ||
31 | static inline void rwsem_clear_owner(struct rw_semaphore *sem) | |
32 | { | |
33 | } | |
34 | #endif | |
35 | ||
c4e05116 IM |
36 | /* |
37 | * lock for reading | |
38 | */ | |
c7af77b5 | 39 | void __sched down_read(struct rw_semaphore *sem) |
c4e05116 IM |
40 | { |
41 | might_sleep(); | |
42 | rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); | |
43 | ||
4fe87745 | 44 | LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
c4e05116 IM |
45 | } |
46 | ||
47 | EXPORT_SYMBOL(down_read); | |
48 | ||
49 | /* | |
50 | * trylock for reading -- returns 1 if successful, 0 if contention | |
51 | */ | |
52 | int down_read_trylock(struct rw_semaphore *sem) | |
53 | { | |
54 | int ret = __down_read_trylock(sem); | |
55 | ||
56 | if (ret == 1) | |
57 | rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); | |
58 | return ret; | |
59 | } | |
60 | ||
61 | EXPORT_SYMBOL(down_read_trylock); | |
62 | ||
63 | /* | |
64 | * lock for writing | |
65 | */ | |
c7af77b5 | 66 | void __sched down_write(struct rw_semaphore *sem) |
c4e05116 IM |
67 | { |
68 | might_sleep(); | |
69 | rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); | |
70 | ||
4fe87745 | 71 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
4fc828e2 | 72 | rwsem_set_owner(sem); |
c4e05116 IM |
73 | } |
74 | ||
75 | EXPORT_SYMBOL(down_write); | |
76 | ||
77 | /* | |
78 | * trylock for writing -- returns 1 if successful, 0 if contention | |
79 | */ | |
80 | int down_write_trylock(struct rw_semaphore *sem) | |
81 | { | |
82 | int ret = __down_write_trylock(sem); | |
83 | ||
4fc828e2 | 84 | if (ret == 1) { |
428e6ce0 | 85 | rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); |
4fc828e2 DB |
86 | rwsem_set_owner(sem); |
87 | } | |
88 | ||
c4e05116 IM |
89 | return ret; |
90 | } | |
91 | ||
92 | EXPORT_SYMBOL(down_write_trylock); | |
93 | ||
94 | /* | |
95 | * release a read lock | |
96 | */ | |
97 | void up_read(struct rw_semaphore *sem) | |
98 | { | |
99 | rwsem_release(&sem->dep_map, 1, _RET_IP_); | |
100 | ||
101 | __up_read(sem); | |
102 | } | |
103 | ||
104 | EXPORT_SYMBOL(up_read); | |
105 | ||
106 | /* | |
107 | * release a write lock | |
108 | */ | |
109 | void up_write(struct rw_semaphore *sem) | |
110 | { | |
111 | rwsem_release(&sem->dep_map, 1, _RET_IP_); | |
112 | ||
4fc828e2 | 113 | rwsem_clear_owner(sem); |
c4e05116 IM |
114 | __up_write(sem); |
115 | } | |
116 | ||
117 | EXPORT_SYMBOL(up_write); | |
118 | ||
119 | /* | |
120 | * downgrade write lock to read lock | |
121 | */ | |
122 | void downgrade_write(struct rw_semaphore *sem) | |
123 | { | |
124 | /* | |
125 | * lockdep: a downgraded write will live on as a write | |
126 | * dependency. | |
127 | */ | |
4fc828e2 | 128 | rwsem_clear_owner(sem); |
c4e05116 IM |
129 | __downgrade_write(sem); |
130 | } | |
131 | ||
132 | EXPORT_SYMBOL(downgrade_write); | |
4ea2176d IM |
133 | |
134 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
135 | ||
136 | void down_read_nested(struct rw_semaphore *sem, int subclass) | |
137 | { | |
138 | might_sleep(); | |
139 | rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); | |
140 | ||
4fe87745 | 141 | LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
4ea2176d IM |
142 | } |
143 | ||
144 | EXPORT_SYMBOL(down_read_nested); | |
145 | ||
1b963c81 JK |
146 | void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest) |
147 | { | |
148 | might_sleep(); | |
149 | rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_); | |
150 | ||
151 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); | |
4fc828e2 | 152 | rwsem_set_owner(sem); |
1b963c81 JK |
153 | } |
154 | ||
155 | EXPORT_SYMBOL(_down_write_nest_lock); | |
156 | ||
84759c6d KO |
157 | void down_read_non_owner(struct rw_semaphore *sem) |
158 | { | |
159 | might_sleep(); | |
160 | ||
161 | __down_read(sem); | |
162 | } | |
163 | ||
164 | EXPORT_SYMBOL(down_read_non_owner); | |
165 | ||
4ea2176d IM |
166 | void down_write_nested(struct rw_semaphore *sem, int subclass) |
167 | { | |
168 | might_sleep(); | |
169 | rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); | |
170 | ||
4fe87745 | 171 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
4fc828e2 | 172 | rwsem_set_owner(sem); |
4ea2176d IM |
173 | } |
174 | ||
175 | EXPORT_SYMBOL(down_write_nested); | |
176 | ||
84759c6d KO |
177 | void up_read_non_owner(struct rw_semaphore *sem) |
178 | { | |
179 | __up_read(sem); | |
180 | } | |
181 | ||
182 | EXPORT_SYMBOL(up_read_non_owner); | |
183 | ||
4ea2176d IM |
184 | #endif |
185 | ||
186 |