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1 // SPDX-License-Identifier: GPL-2.0
2 /* kernel/rwsem.c: R/W semaphores, public implementation
3 *
4 * Written by David Howells (dhowells@redhat.com).
5 * Derived from asm-i386/semaphore.h
6 */
7
8 #include <linux/types.h>
9 #include <linux/kernel.h>
10 #include <linux/sched.h>
11 #include <linux/sched/debug.h>
12 #include <linux/export.h>
13 #include <linux/rwsem.h>
14 #include <linux/atomic.h>
15
16 #include "rwsem.h"
17
18 /*
19 * lock for reading
20 */
21 void __sched down_read(struct rw_semaphore *sem)
22 {
23 might_sleep();
24 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
25
26 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
27 rwsem_set_reader_owned(sem);
28 }
29
30 EXPORT_SYMBOL(down_read);
31
32 int __sched down_read_killable(struct rw_semaphore *sem)
33 {
34 might_sleep();
35 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
36
37 if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_killable)) {
38 rwsem_release(&sem->dep_map, 1, _RET_IP_);
39 return -EINTR;
40 }
41
42 rwsem_set_reader_owned(sem);
43 return 0;
44 }
45
46 EXPORT_SYMBOL(down_read_killable);
47
48 /*
49 * trylock for reading -- returns 1 if successful, 0 if contention
50 */
51 int down_read_trylock(struct rw_semaphore *sem)
52 {
53 int ret = __down_read_trylock(sem);
54
55 if (ret == 1) {
56 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
57 rwsem_set_reader_owned(sem);
58 }
59 return ret;
60 }
61
62 EXPORT_SYMBOL(down_read_trylock);
63
64 /*
65 * lock for writing
66 */
67 void __sched down_write(struct rw_semaphore *sem)
68 {
69 might_sleep();
70 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
71
72 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
73 rwsem_set_owner(sem);
74 }
75
76 EXPORT_SYMBOL(down_write);
77
78 /*
79 * lock for writing
80 */
81 int __sched down_write_killable(struct rw_semaphore *sem)
82 {
83 might_sleep();
84 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
85
86 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
87 rwsem_release(&sem->dep_map, 1, _RET_IP_);
88 return -EINTR;
89 }
90
91 rwsem_set_owner(sem);
92 return 0;
93 }
94
95 EXPORT_SYMBOL(down_write_killable);
96
97 /*
98 * trylock for writing -- returns 1 if successful, 0 if contention
99 */
100 int down_write_trylock(struct rw_semaphore *sem)
101 {
102 int ret = __down_write_trylock(sem);
103
104 if (ret == 1) {
105 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
106 rwsem_set_owner(sem);
107 }
108
109 return ret;
110 }
111
112 EXPORT_SYMBOL(down_write_trylock);
113
114 /*
115 * release a read lock
116 */
117 void up_read(struct rw_semaphore *sem)
118 {
119 rwsem_release(&sem->dep_map, 1, _RET_IP_);
120
121 __up_read(sem);
122 }
123
124 EXPORT_SYMBOL(up_read);
125
126 /*
127 * release a write lock
128 */
129 void up_write(struct rw_semaphore *sem)
130 {
131 rwsem_release(&sem->dep_map, 1, _RET_IP_);
132
133 rwsem_clear_owner(sem);
134 __up_write(sem);
135 }
136
137 EXPORT_SYMBOL(up_write);
138
139 /*
140 * downgrade write lock to read lock
141 */
142 void downgrade_write(struct rw_semaphore *sem)
143 {
144 lock_downgrade(&sem->dep_map, _RET_IP_);
145
146 rwsem_set_reader_owned(sem);
147 __downgrade_write(sem);
148 }
149
150 EXPORT_SYMBOL(downgrade_write);
151
152 #ifdef CONFIG_DEBUG_LOCK_ALLOC
153
154 void down_read_nested(struct rw_semaphore *sem, int subclass)
155 {
156 might_sleep();
157 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
158
159 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
160 rwsem_set_reader_owned(sem);
161 }
162
163 EXPORT_SYMBOL(down_read_nested);
164
165 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
166 {
167 might_sleep();
168 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
169
170 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
171 rwsem_set_owner(sem);
172 }
173
174 EXPORT_SYMBOL(_down_write_nest_lock);
175
176 void down_read_non_owner(struct rw_semaphore *sem)
177 {
178 might_sleep();
179
180 __down_read(sem);
181 }
182
183 EXPORT_SYMBOL(down_read_non_owner);
184
185 void down_write_nested(struct rw_semaphore *sem, int subclass)
186 {
187 might_sleep();
188 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
189
190 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
191 rwsem_set_owner(sem);
192 }
193
194 EXPORT_SYMBOL(down_write_nested);
195
196 int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
197 {
198 might_sleep();
199 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
200
201 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
202 rwsem_release(&sem->dep_map, 1, _RET_IP_);
203 return -EINTR;
204 }
205
206 rwsem_set_owner(sem);
207 return 0;
208 }
209
210 EXPORT_SYMBOL(down_write_killable_nested);
211
212 void up_read_non_owner(struct rw_semaphore *sem)
213 {
214 __up_read(sem);
215 }
216
217 EXPORT_SYMBOL(up_read_non_owner);
218
219 #endif