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 */
down_read(struct rw_semaphore * sem)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
down_read_killable(struct rw_semaphore * sem)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 */
down_read_trylock(struct rw_semaphore * sem)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 */
down_write(struct rw_semaphore * sem)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 */
down_write_killable(struct rw_semaphore * sem)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 */
down_write_trylock(struct rw_semaphore * sem)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 */
up_read(struct rw_semaphore * sem)117 void up_read(struct rw_semaphore *sem)
118 {
119 rwsem_release(&sem->dep_map, 1, _RET_IP_);
120 DEBUG_RWSEMS_WARN_ON(sem->owner != RWSEM_READER_OWNED);
121
122 __up_read(sem);
123 }
124
125 EXPORT_SYMBOL(up_read);
126
127 /*
128 * release a write lock
129 */
up_write(struct rw_semaphore * sem)130 void up_write(struct rw_semaphore *sem)
131 {
132 rwsem_release(&sem->dep_map, 1, _RET_IP_);
133 DEBUG_RWSEMS_WARN_ON(sem->owner != current);
134
135 rwsem_clear_owner(sem);
136 __up_write(sem);
137 }
138
139 EXPORT_SYMBOL(up_write);
140
141 /*
142 * downgrade write lock to read lock
143 */
downgrade_write(struct rw_semaphore * sem)144 void downgrade_write(struct rw_semaphore *sem)
145 {
146 lock_downgrade(&sem->dep_map, _RET_IP_);
147 DEBUG_RWSEMS_WARN_ON(sem->owner != current);
148
149 rwsem_set_reader_owned(sem);
150 __downgrade_write(sem);
151 }
152
153 EXPORT_SYMBOL(downgrade_write);
154
155 #ifdef CONFIG_DEBUG_LOCK_ALLOC
156
down_read_nested(struct rw_semaphore * sem,int subclass)157 void down_read_nested(struct rw_semaphore *sem, int subclass)
158 {
159 might_sleep();
160 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
161
162 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
163 rwsem_set_reader_owned(sem);
164 }
165
166 EXPORT_SYMBOL(down_read_nested);
167
_down_write_nest_lock(struct rw_semaphore * sem,struct lockdep_map * nest)168 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
169 {
170 might_sleep();
171 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
172
173 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
174 rwsem_set_owner(sem);
175 }
176
177 EXPORT_SYMBOL(_down_write_nest_lock);
178
down_read_non_owner(struct rw_semaphore * sem)179 void down_read_non_owner(struct rw_semaphore *sem)
180 {
181 might_sleep();
182
183 __down_read(sem);
184 rwsem_set_reader_owned(sem);
185 }
186
187 EXPORT_SYMBOL(down_read_non_owner);
188
down_write_nested(struct rw_semaphore * sem,int subclass)189 void down_write_nested(struct rw_semaphore *sem, int subclass)
190 {
191 might_sleep();
192 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
193
194 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
195 rwsem_set_owner(sem);
196 }
197
198 EXPORT_SYMBOL(down_write_nested);
199
down_write_killable_nested(struct rw_semaphore * sem,int subclass)200 int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
201 {
202 might_sleep();
203 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
204
205 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
206 rwsem_release(&sem->dep_map, 1, _RET_IP_);
207 return -EINTR;
208 }
209
210 rwsem_set_owner(sem);
211 return 0;
212 }
213
214 EXPORT_SYMBOL(down_write_killable_nested);
215
up_read_non_owner(struct rw_semaphore * sem)216 void up_read_non_owner(struct rw_semaphore *sem)
217 {
218 DEBUG_RWSEMS_WARN_ON(sem->owner != RWSEM_READER_OWNED);
219 __up_read(sem);
220 }
221
222 EXPORT_SYMBOL(up_read_non_owner);
223
224 #endif
225
