projects/linux·blob v4.2 · refs

166 lines · 3.0 KiB

1/* kernel/rwsem.c: R/W semaphores, public implementation
2 *
3 * Written by David Howells ([email protected]).
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#include <linux/atomic.h>
13
14#include "rwsem.h"
15
16/*
17 * lock for reading
18 */
19void __sched down_read(struct rw_semaphore *sem)
20{
21 might_sleep();
22 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
23
24 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
25}
26
27EXPORT_SYMBOL(down_read);
28
29/*
30 * trylock for reading -- returns 1 if successful, 0 if contention
31 */
32int down_read_trylock(struct rw_semaphore *sem)
33{
34 int ret = __down_read_trylock(sem);
35
36 if (ret == 1)
37 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
38 return ret;
39}
40
41EXPORT_SYMBOL(down_read_trylock);
42
43/*
44 * lock for writing
45 */
46void __sched down_write(struct rw_semaphore *sem)
47{
48 might_sleep();
49 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
50
51 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
52 rwsem_set_owner(sem);
53}
54
55EXPORT_SYMBOL(down_write);
56
57/*
58 * trylock for writing -- returns 1 if successful, 0 if contention
59 */
60int down_write_trylock(struct rw_semaphore *sem)
61{
62 int ret = __down_write_trylock(sem);
63
64 if (ret == 1) {
65 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
66 rwsem_set_owner(sem);
67 }
68
69 return ret;
70}
71
72EXPORT_SYMBOL(down_write_trylock);
73
74/*
75 * release a read lock
76 */
77void up_read(struct rw_semaphore *sem)
78{
79 rwsem_release(&sem->dep_map, 1, _RET_IP_);
80
81 __up_read(sem);
82}
83
84EXPORT_SYMBOL(up_read);
85
86/*
87 * release a write lock
88 */
89void up_write(struct rw_semaphore *sem)
90{
91 rwsem_release(&sem->dep_map, 1, _RET_IP_);
92
93 rwsem_clear_owner(sem);
94 __up_write(sem);
95}
96
97EXPORT_SYMBOL(up_write);
98
99/*
100 * downgrade write lock to read lock
101 */
102void downgrade_write(struct rw_semaphore *sem)
103{
104 /*
105 * lockdep: a downgraded write will live on as a write
106 * dependency.
107 */
108 rwsem_clear_owner(sem);
109 __downgrade_write(sem);
110}
111
112EXPORT_SYMBOL(downgrade_write);
113
114#ifdef CONFIG_DEBUG_LOCK_ALLOC
115
116void down_read_nested(struct rw_semaphore *sem, int subclass)
117{
118 might_sleep();
119 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
120
121 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
122}
123
124EXPORT_SYMBOL(down_read_nested);
125
126void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
127{
128 might_sleep();
129 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
130
131 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
132 rwsem_set_owner(sem);
133}
134
135EXPORT_SYMBOL(_down_write_nest_lock);
136
137void down_read_non_owner(struct rw_semaphore *sem)
138{
139 might_sleep();
140
141 __down_read(sem);
142}
143
144EXPORT_SYMBOL(down_read_non_owner);
145
146void down_write_nested(struct rw_semaphore *sem, int subclass)
147{
148 might_sleep();
149 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
150
151 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
152 rwsem_set_owner(sem);
153}
154
155EXPORT_SYMBOL(down_write_nested);
156
157void up_read_non_owner(struct rw_semaphore *sem)
158{
159 __up_read(sem);
160}
161
162EXPORT_SYMBOL(up_read_non_owner);
163
164#endif
165
166