projects/linux·blob v4.20 · refs

225 lines · 4.5 KiB

1// SPDX-License-Identifier: GPL-2.0
2/* kernel/rwsem.c: R/W semaphores, public implementation
3 *
4 * Written by David Howells ([email protected]).
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(!((unsigned long)sem->owner & RWSEM_READER_OWNED));
121
122 rwsem_clear_reader_owned(sem);
123 __up_read(sem);
124}
125
126EXPORT_SYMBOL(up_read);
127
128/*
129 * release a write lock
130 */
131void up_write(struct rw_semaphore *sem)
132{
133 rwsem_release(&sem->dep_map, 1, _RET_IP_);
134 DEBUG_RWSEMS_WARN_ON(sem->owner != current);
135
136 rwsem_clear_owner(sem);
137 __up_write(sem);
138}
139
140EXPORT_SYMBOL(up_write);
141
142/*
143 * downgrade write lock to read lock
144 */
145void downgrade_write(struct rw_semaphore *sem)
146{
147 lock_downgrade(&sem->dep_map, _RET_IP_);
148 DEBUG_RWSEMS_WARN_ON(sem->owner != current);
149
150 rwsem_set_reader_owned(sem);
151 __downgrade_write(sem);
152}
153
154EXPORT_SYMBOL(downgrade_write);
155
156#ifdef CONFIG_DEBUG_LOCK_ALLOC
157
158void down_read_nested(struct rw_semaphore *sem, int subclass)
159{
160 might_sleep();
161 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
162
163 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
164 rwsem_set_reader_owned(sem);
165}
166
167EXPORT_SYMBOL(down_read_nested);
168
169void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
170{
171 might_sleep();
172 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
173
174 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
175 rwsem_set_owner(sem);
176}
177
178EXPORT_SYMBOL(_down_write_nest_lock);
179
180void down_read_non_owner(struct rw_semaphore *sem)
181{
182 might_sleep();
183
184 __down_read(sem);
185 __rwsem_set_reader_owned(sem, NULL);
186}
187
188EXPORT_SYMBOL(down_read_non_owner);
189
190void down_write_nested(struct rw_semaphore *sem, int subclass)
191{
192 might_sleep();
193 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
194
195 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
196 rwsem_set_owner(sem);
197}
198
199EXPORT_SYMBOL(down_write_nested);
200
201int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
202{
203 might_sleep();
204 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
205
206 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
207 rwsem_release(&sem->dep_map, 1, _RET_IP_);
208 return -EINTR;
209 }
210
211 rwsem_set_owner(sem);
212 return 0;
213}
214
215EXPORT_SYMBOL(down_write_killable_nested);
216
217void up_read_non_owner(struct rw_semaphore *sem)
218{
219 DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED));
220 __up_read(sem);
221}
222
223EXPORT_SYMBOL(up_read_non_owner);
224
225#endif