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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 | 11 | #include <linux/rwsem.h> |
60063497 | 12 | #include <linux/atomic.h> |
c4e05116 | 13 | |
7a215f89 | 14 | #include "rwsem.h" |
4fc828e2 | 15 | |
c4e05116 IM |
16 | /* |
17 | * lock for reading | |
18 | */ | |
c7af77b5 | 19 | void __sched down_read(struct rw_semaphore *sem) |
c4e05116 IM |
20 | { |
21 | might_sleep(); | |
22 | rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); | |
23 | ||
4fe87745 | 24 | LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
19c5d690 | 25 | rwsem_set_reader_owned(sem); |
c4e05116 IM |
26 | } |
27 | ||
28 | EXPORT_SYMBOL(down_read); | |
29 | ||
30 | /* | |
31 | * trylock for reading -- returns 1 if successful, 0 if contention | |
32 | */ | |
33 | int down_read_trylock(struct rw_semaphore *sem) | |
34 | { | |
35 | int ret = __down_read_trylock(sem); | |
36 | ||
19c5d690 | 37 | if (ret == 1) { |
c4e05116 | 38 | rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); |
19c5d690 WL |
39 | rwsem_set_reader_owned(sem); |
40 | } | |
c4e05116 IM |
41 | return ret; |
42 | } | |
43 | ||
44 | EXPORT_SYMBOL(down_read_trylock); | |
45 | ||
46 | /* | |
47 | * lock for writing | |
48 | */ | |
c7af77b5 | 49 | void __sched down_write(struct rw_semaphore *sem) |
c4e05116 IM |
50 | { |
51 | might_sleep(); | |
52 | rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); | |
53 | ||
4fe87745 | 54 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
4fc828e2 | 55 | rwsem_set_owner(sem); |
c4e05116 IM |
56 | } |
57 | ||
58 | EXPORT_SYMBOL(down_write); | |
59 | ||
916633a4 MH |
60 | /* |
61 | * lock for writing | |
62 | */ | |
63 | int __sched down_write_killable(struct rw_semaphore *sem) | |
64 | { | |
65 | might_sleep(); | |
66 | rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); | |
67 | ||
68 | if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) { | |
69 | rwsem_release(&sem->dep_map, 1, _RET_IP_); | |
70 | return -EINTR; | |
71 | } | |
72 | ||
73 | rwsem_set_owner(sem); | |
74 | return 0; | |
75 | } | |
76 | ||
77 | EXPORT_SYMBOL(down_write_killable); | |
78 | ||
c4e05116 IM |
79 | /* |
80 | * trylock for writing -- returns 1 if successful, 0 if contention | |
81 | */ | |
82 | int down_write_trylock(struct rw_semaphore *sem) | |
83 | { | |
84 | int ret = __down_write_trylock(sem); | |
85 | ||
4fc828e2 | 86 | if (ret == 1) { |
428e6ce0 | 87 | rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); |
4fc828e2 DB |
88 | rwsem_set_owner(sem); |
89 | } | |
90 | ||
c4e05116 IM |
91 | return ret; |
92 | } | |
93 | ||
94 | EXPORT_SYMBOL(down_write_trylock); | |
95 | ||
96 | /* | |
97 | * release a read lock | |
98 | */ | |
99 | void up_read(struct rw_semaphore *sem) | |
100 | { | |
101 | rwsem_release(&sem->dep_map, 1, _RET_IP_); | |
102 | ||
103 | __up_read(sem); | |
104 | } | |
105 | ||
106 | EXPORT_SYMBOL(up_read); | |
107 | ||
108 | /* | |
109 | * release a write lock | |
110 | */ | |
111 | void up_write(struct rw_semaphore *sem) | |
112 | { | |
113 | rwsem_release(&sem->dep_map, 1, _RET_IP_); | |
114 | ||
4fc828e2 | 115 | rwsem_clear_owner(sem); |
c4e05116 IM |
116 | __up_write(sem); |
117 | } | |
118 | ||
119 | EXPORT_SYMBOL(up_write); | |
120 | ||
121 | /* | |
122 | * downgrade write lock to read lock | |
123 | */ | |
124 | void downgrade_write(struct rw_semaphore *sem) | |
125 | { | |
126 | /* | |
127 | * lockdep: a downgraded write will live on as a write | |
128 | * dependency. | |
129 | */ | |
19c5d690 | 130 | rwsem_set_reader_owned(sem); |
c4e05116 IM |
131 | __downgrade_write(sem); |
132 | } | |
133 | ||
134 | EXPORT_SYMBOL(downgrade_write); | |
4ea2176d IM |
135 | |
136 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
137 | ||
138 | void down_read_nested(struct rw_semaphore *sem, int subclass) | |
139 | { | |
140 | might_sleep(); | |
141 | rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); | |
142 | ||
4fe87745 | 143 | LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
19c5d690 | 144 | rwsem_set_reader_owned(sem); |
4ea2176d IM |
145 | } |
146 | ||
147 | EXPORT_SYMBOL(down_read_nested); | |
148 | ||
1b963c81 JK |
149 | void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest) |
150 | { | |
151 | might_sleep(); | |
152 | rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_); | |
153 | ||
154 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); | |
4fc828e2 | 155 | rwsem_set_owner(sem); |
1b963c81 JK |
156 | } |
157 | ||
158 | EXPORT_SYMBOL(_down_write_nest_lock); | |
159 | ||
84759c6d KO |
160 | void down_read_non_owner(struct rw_semaphore *sem) |
161 | { | |
162 | might_sleep(); | |
163 | ||
164 | __down_read(sem); | |
165 | } | |
166 | ||
167 | EXPORT_SYMBOL(down_read_non_owner); | |
168 | ||
4ea2176d IM |
169 | void down_write_nested(struct rw_semaphore *sem, int subclass) |
170 | { | |
171 | might_sleep(); | |
172 | rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); | |
173 | ||
4fe87745 | 174 | LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
4fc828e2 | 175 | rwsem_set_owner(sem); |
4ea2176d IM |
176 | } |
177 | ||
178 | EXPORT_SYMBOL(down_write_nested); | |
179 | ||
887bddfa AV |
180 | int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass) |
181 | { | |
182 | might_sleep(); | |
183 | rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); | |
184 | ||
185 | if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) { | |
186 | rwsem_release(&sem->dep_map, 1, _RET_IP_); | |
187 | return -EINTR; | |
188 | } | |
189 | ||
190 | rwsem_set_owner(sem); | |
191 | return 0; | |
192 | } | |
193 | ||
194 | EXPORT_SYMBOL(down_write_killable_nested); | |
195 | ||
84759c6d KO |
196 | void up_read_non_owner(struct rw_semaphore *sem) |
197 | { | |
198 | __up_read(sem); | |
199 | } | |
200 | ||
201 | EXPORT_SYMBOL(up_read_non_owner); | |
202 | ||
4ea2176d IM |
203 | #endif |
204 | ||
205 |