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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 */
21void __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
30EXPORT_SYMBOL(down_read);
31
32int __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
46EXPORT_SYMBOL(down_read_killable);
47
48/*
49 * trylock for reading -- returns 1 if successful, 0 if contention
50 */
51int 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
62EXPORT_SYMBOL(down_read_trylock);
63
64/*
65 * lock for writing
66 */
67void __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
76EXPORT_SYMBOL(down_write);
77
78/*
79 * lock for writing
80 */
81int __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
95EXPORT_SYMBOL(down_write_killable);
96
97/*
98 * trylock for writing -- returns 1 if successful, 0 if contention
99 */
100int 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
112EXPORT_SYMBOL(down_write_trylock);
113
114/*
115 * release a read lock
116 */
117void 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
125EXPORT_SYMBOL(up_read);
126
127/*
128 * release a write lock
129 */
130void 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
139EXPORT_SYMBOL(up_write);
140
141/*
142 * downgrade write lock to read lock
143 */
144void 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
153EXPORT_SYMBOL(downgrade_write);
154
155#ifdef CONFIG_DEBUG_LOCK_ALLOC
156
157void 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
166EXPORT_SYMBOL(down_read_nested);
167
168void _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
177EXPORT_SYMBOL(_down_write_nest_lock);
178
179void down_read_non_owner(struct rw_semaphore *sem)
180{
181 might_sleep();
182
183 __down_read(sem);
184}
185
186EXPORT_SYMBOL(down_read_non_owner);
187
188void down_write_nested(struct rw_semaphore *sem, int subclass)
189{
190 might_sleep();
191 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
192
193 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
194 rwsem_set_owner(sem);
195}
196
197EXPORT_SYMBOL(down_write_nested);
198
199int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
200{
201 might_sleep();
202 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
203
204 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
205 rwsem_release(&sem->dep_map, 1, _RET_IP_);
206 return -EINTR;
207 }
208
209 rwsem_set_owner(sem);
210 return 0;
211}
212
213EXPORT_SYMBOL(down_write_killable_nested);
214
215void up_read_non_owner(struct rw_semaphore *sem)
216{
217 DEBUG_RWSEMS_WARN_ON(sem->owner != RWSEM_READER_OWNED);
218 __up_read(sem);
219}
220
221EXPORT_SYMBOL(up_read_non_owner);
222
223#endif
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>
9#include <linux/sched.h>
10#include <linux/export.h>
11#include <linux/rwsem.h>
12
13#include <linux/atomic.h>
14
15/*
16 * lock for reading
17 */
18void __sched down_read(struct rw_semaphore *sem)
19{
20 might_sleep();
21 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
22
23 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
24}
25
26EXPORT_SYMBOL(down_read);
27
28/*
29 * trylock for reading -- returns 1 if successful, 0 if contention
30 */
31int down_read_trylock(struct rw_semaphore *sem)
32{
33 int ret = __down_read_trylock(sem);
34
35 if (ret == 1)
36 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
37 return ret;
38}
39
40EXPORT_SYMBOL(down_read_trylock);
41
42/*
43 * lock for writing
44 */
45void __sched down_write(struct rw_semaphore *sem)
46{
47 might_sleep();
48 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
49
50 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
51}
52
53EXPORT_SYMBOL(down_write);
54
55/*
56 * trylock for writing -- returns 1 if successful, 0 if contention
57 */
58int down_write_trylock(struct rw_semaphore *sem)
59{
60 int ret = __down_write_trylock(sem);
61
62 if (ret == 1)
63 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
64 return ret;
65}
66
67EXPORT_SYMBOL(down_write_trylock);
68
69/*
70 * release a read lock
71 */
72void up_read(struct rw_semaphore *sem)
73{
74 rwsem_release(&sem->dep_map, 1, _RET_IP_);
75
76 __up_read(sem);
77}
78
79EXPORT_SYMBOL(up_read);
80
81/*
82 * release a write lock
83 */
84void up_write(struct rw_semaphore *sem)
85{
86 rwsem_release(&sem->dep_map, 1, _RET_IP_);
87
88 __up_write(sem);
89}
90
91EXPORT_SYMBOL(up_write);
92
93/*
94 * downgrade write lock to read lock
95 */
96void downgrade_write(struct rw_semaphore *sem)
97{
98 /*
99 * lockdep: a downgraded write will live on as a write
100 * dependency.
101 */
102 __downgrade_write(sem);
103}
104
105EXPORT_SYMBOL(downgrade_write);
106
107#ifdef CONFIG_DEBUG_LOCK_ALLOC
108
109void down_read_nested(struct rw_semaphore *sem, int subclass)
110{
111 might_sleep();
112 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
113
114 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
115}
116
117EXPORT_SYMBOL(down_read_nested);
118
119void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
120{
121 might_sleep();
122 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
123
124 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
125}
126
127EXPORT_SYMBOL(_down_write_nest_lock);
128
129void down_read_non_owner(struct rw_semaphore *sem)
130{
131 might_sleep();
132
133 __down_read(sem);
134}
135
136EXPORT_SYMBOL(down_read_non_owner);
137
138void down_write_nested(struct rw_semaphore *sem, int subclass)
139{
140 might_sleep();
141 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
142
143 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
144}
145
146EXPORT_SYMBOL(down_write_nested);
147
148void up_read_non_owner(struct rw_semaphore *sem)
149{
150 __up_read(sem);
151}
152
153EXPORT_SYMBOL(up_read_non_owner);
154
155#endif
156
157