projects/linux·blob v3.0 · refs

148 lines · 2.6 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/module.h>
11#include <linux/rwsem.h>
12
13#include <asm/system.h>
14#include <asm/atomic.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}
53
54EXPORT_SYMBOL(down_write);
55
56/*
57 * trylock for writing -- returns 1 if successful, 0 if contention
58 */
59int down_write_trylock(struct rw_semaphore *sem)
60{
61 int ret = __down_write_trylock(sem);
62
63 if (ret == 1)
64 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
65 return ret;
66}
67
68EXPORT_SYMBOL(down_write_trylock);
69
70/*
71 * release a read lock
72 */
73void up_read(struct rw_semaphore *sem)
74{
75 rwsem_release(&sem->dep_map, 1, _RET_IP_);
76
77 __up_read(sem);
78}
79
80EXPORT_SYMBOL(up_read);
81
82/*
83 * release a write lock
84 */
85void up_write(struct rw_semaphore *sem)
86{
87 rwsem_release(&sem->dep_map, 1, _RET_IP_);
88
89 __up_write(sem);
90}
91
92EXPORT_SYMBOL(up_write);
93
94/*
95 * downgrade write lock to read lock
96 */
97void downgrade_write(struct rw_semaphore *sem)
98{
99 /*
100 * lockdep: a downgraded write will live on as a write
101 * dependency.
102 */
103 __downgrade_write(sem);
104}
105
106EXPORT_SYMBOL(downgrade_write);
107
108#ifdef CONFIG_DEBUG_LOCK_ALLOC
109
110void down_read_nested(struct rw_semaphore *sem, int subclass)
111{
112 might_sleep();
113 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
114
115 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
116}
117
118EXPORT_SYMBOL(down_read_nested);
119
120void down_read_non_owner(struct rw_semaphore *sem)
121{
122 might_sleep();
123
124 __down_read(sem);
125}
126
127EXPORT_SYMBOL(down_read_non_owner);
128
129void down_write_nested(struct rw_semaphore *sem, int subclass)
130{
131 might_sleep();
132 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
133
134 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
135}
136
137EXPORT_SYMBOL(down_write_nested);
138
139void up_read_non_owner(struct rw_semaphore *sem)
140{
141 __up_read(sem);
142}
143
144EXPORT_SYMBOL(up_read_non_owner);
145
146#endif
147
148