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