projects/linux·blob v4.11 · refs

206 lines · 3.8 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/sched/debug.h>
11#include <linux/export.h>
12#include <linux/rwsem.h>
13#include <linux/atomic.h>
14
15#include "rwsem.h"
16
17/*
18 * lock for reading
19 */
20void __sched down_read(struct rw_semaphore *sem)
21{
22 might_sleep();
23 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
24
25 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
26 rwsem_set_reader_owned(sem);
27}
28
29EXPORT_SYMBOL(down_read);
30
31/*
32 * trylock for reading -- returns 1 if successful, 0 if contention
33 */
34int down_read_trylock(struct rw_semaphore *sem)
35{
36 int ret = __down_read_trylock(sem);
37
38 if (ret == 1) {
39 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
40 rwsem_set_reader_owned(sem);
41 }
42 return ret;
43}
44
45EXPORT_SYMBOL(down_read_trylock);
46
47/*
48 * lock for writing
49 */
50void __sched down_write(struct rw_semaphore *sem)
51{
52 might_sleep();
53 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
54
55 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
56 rwsem_set_owner(sem);
57}
58
59EXPORT_SYMBOL(down_write);
60
61/*
62 * lock for writing
63 */
64int __sched down_write_killable(struct rw_semaphore *sem)
65{
66 might_sleep();
67 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
68
69 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
70 rwsem_release(&sem->dep_map, 1, _RET_IP_);
71 return -EINTR;
72 }
73
74 rwsem_set_owner(sem);
75 return 0;
76}
77
78EXPORT_SYMBOL(down_write_killable);
79
80/*
81 * trylock for writing -- returns 1 if successful, 0 if contention
82 */
83int down_write_trylock(struct rw_semaphore *sem)
84{
85 int ret = __down_write_trylock(sem);
86
87 if (ret == 1) {
88 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
89 rwsem_set_owner(sem);
90 }
91
92 return ret;
93}
94
95EXPORT_SYMBOL(down_write_trylock);
96
97/*
98 * release a read lock
99 */
100void up_read(struct rw_semaphore *sem)
101{
102 rwsem_release(&sem->dep_map, 1, _RET_IP_);
103
104 __up_read(sem);
105}
106
107EXPORT_SYMBOL(up_read);
108
109/*
110 * release a write lock
111 */
112void up_write(struct rw_semaphore *sem)
113{
114 rwsem_release(&sem->dep_map, 1, _RET_IP_);
115
116 rwsem_clear_owner(sem);
117 __up_write(sem);
118}
119
120EXPORT_SYMBOL(up_write);
121
122/*
123 * downgrade write lock to read lock
124 */
125void downgrade_write(struct rw_semaphore *sem)
126{
127 /*
128 * lockdep: a downgraded write will live on as a write
129 * dependency.
130 */
131 rwsem_set_reader_owned(sem);
132 __downgrade_write(sem);
133}
134
135EXPORT_SYMBOL(downgrade_write);
136
137#ifdef CONFIG_DEBUG_LOCK_ALLOC
138
139void down_read_nested(struct rw_semaphore *sem, int subclass)
140{
141 might_sleep();
142 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
143
144 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
145 rwsem_set_reader_owned(sem);
146}
147
148EXPORT_SYMBOL(down_read_nested);
149
150void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
151{
152 might_sleep();
153 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
154
155 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
156 rwsem_set_owner(sem);
157}
158
159EXPORT_SYMBOL(_down_write_nest_lock);
160
161void down_read_non_owner(struct rw_semaphore *sem)
162{
163 might_sleep();
164
165 __down_read(sem);
166}
167
168EXPORT_SYMBOL(down_read_non_owner);
169
170void down_write_nested(struct rw_semaphore *sem, int subclass)
171{
172 might_sleep();
173 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
174
175 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
176 rwsem_set_owner(sem);
177}
178
179EXPORT_SYMBOL(down_write_nested);
180
181int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
182{
183 might_sleep();
184 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
185
186 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
187 rwsem_release(&sem->dep_map, 1, _RET_IP_);
188 return -EINTR;
189 }
190
191 rwsem_set_owner(sem);
192 return 0;
193}
194
195EXPORT_SYMBOL(down_write_killable_nested);
196
197void up_read_non_owner(struct rw_semaphore *sem)
198{
199 __up_read(sem);
200}
201
202EXPORT_SYMBOL(up_read_non_owner);
203
204#endif
205
206