projects/linux·blob v4.7 · refs

201 lines · 3.7 KiB

1/* kernel/rwsem.c: R/W semaphores, public implementation
2 *
3 * Written by David Howells ([email protected]).
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/export.h>
11#include <linux/rwsem.h>
12#include <linux/atomic.h>
13
14#include "rwsem.h"
15
16/*
17 * lock for reading
18 */
19void __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
27EXPORT_SYMBOL(down_read);
28
29/*
30 * trylock for reading -- returns 1 if successful, 0 if contention
31 */
32int 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
41EXPORT_SYMBOL(down_read_trylock);
42
43/*
44 * lock for writing
45 */
46void __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 rwsem_set_owner(sem);
53}
54
55EXPORT_SYMBOL(down_write);
56
57/*
58 * lock for writing
59 */
60int __sched down_write_killable(struct rw_semaphore *sem)
61{
62 might_sleep();
63 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
64
65 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
66 rwsem_release(&sem->dep_map, 1, _RET_IP_);
67 return -EINTR;
68 }
69
70 rwsem_set_owner(sem);
71 return 0;
72}
73
74EXPORT_SYMBOL(down_write_killable);
75
76/*
77 * trylock for writing -- returns 1 if successful, 0 if contention
78 */
79int down_write_trylock(struct rw_semaphore *sem)
80{
81 int ret = __down_write_trylock(sem);
82
83 if (ret == 1) {
84 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
85 rwsem_set_owner(sem);
86 }
87
88 return ret;
89}
90
91EXPORT_SYMBOL(down_write_trylock);
92
93/*
94 * release a read lock
95 */
96void up_read(struct rw_semaphore *sem)
97{
98 rwsem_release(&sem->dep_map, 1, _RET_IP_);
99
100 __up_read(sem);
101}
102
103EXPORT_SYMBOL(up_read);
104
105/*
106 * release a write lock
107 */
108void up_write(struct rw_semaphore *sem)
109{
110 rwsem_release(&sem->dep_map, 1, _RET_IP_);
111
112 rwsem_clear_owner(sem);
113 __up_write(sem);
114}
115
116EXPORT_SYMBOL(up_write);
117
118/*
119 * downgrade write lock to read lock
120 */
121void downgrade_write(struct rw_semaphore *sem)
122{
123 /*
124 * lockdep: a downgraded write will live on as a write
125 * dependency.
126 */
127 rwsem_clear_owner(sem);
128 __downgrade_write(sem);
129}
130
131EXPORT_SYMBOL(downgrade_write);
132
133#ifdef CONFIG_DEBUG_LOCK_ALLOC
134
135void down_read_nested(struct rw_semaphore *sem, int subclass)
136{
137 might_sleep();
138 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
139
140 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
141}
142
143EXPORT_SYMBOL(down_read_nested);
144
145void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
146{
147 might_sleep();
148 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
149
150 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
151 rwsem_set_owner(sem);
152}
153
154EXPORT_SYMBOL(_down_write_nest_lock);
155
156void down_read_non_owner(struct rw_semaphore *sem)
157{
158 might_sleep();
159
160 __down_read(sem);
161}
162
163EXPORT_SYMBOL(down_read_non_owner);
164
165void down_write_nested(struct rw_semaphore *sem, int subclass)
166{
167 might_sleep();
168 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
169
170 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
171 rwsem_set_owner(sem);
172}
173
174EXPORT_SYMBOL(down_write_nested);
175
176int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
177{
178 might_sleep();
179 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
180
181 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
182 rwsem_release(&sem->dep_map, 1, _RET_IP_);
183 return -EINTR;
184 }
185
186 rwsem_set_owner(sem);
187 return 0;
188}
189
190EXPORT_SYMBOL(down_write_killable_nested);
191
192void up_read_non_owner(struct rw_semaphore *sem)
193{
194 __up_read(sem);
195}
196
197EXPORT_SYMBOL(up_read_non_owner);
198
199#endif
200
201