ARM: tegra: dvfs: Add GPU scaling trip-points interfaces
[linux-3.10.git] / kernel / rwsem.c
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  */
18 void __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
26 EXPORT_SYMBOL(down_read);
27
28 /*
29  * trylock for reading -- returns 1 if successful, 0 if contention
30  */
31 int 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
40 EXPORT_SYMBOL(down_read_trylock);
41
42 /*
43  * lock for writing
44  */
45 void __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
53 EXPORT_SYMBOL(down_write);
54
55 /*
56  * trylock for writing -- returns 1 if successful, 0 if contention
57  */
58 int 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
67 EXPORT_SYMBOL(down_write_trylock);
68
69 /*
70  * release a read lock
71  */
72 void up_read(struct rw_semaphore *sem)
73 {
74         rwsem_release(&sem->dep_map, 1, _RET_IP_);
75
76         __up_read(sem);
77 }
78
79 EXPORT_SYMBOL(up_read);
80
81 /*
82  * release a write lock
83  */
84 void up_write(struct rw_semaphore *sem)
85 {
86         rwsem_release(&sem->dep_map, 1, _RET_IP_);
87
88         __up_write(sem);
89 }
90
91 EXPORT_SYMBOL(up_write);
92
93 /*
94  * downgrade write lock to read lock
95  */
96 void 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
105 EXPORT_SYMBOL(downgrade_write);
106
107 #ifdef CONFIG_DEBUG_LOCK_ALLOC
108
109 void 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
117 EXPORT_SYMBOL(down_read_nested);
118
119 void _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
127 EXPORT_SYMBOL(_down_write_nest_lock);
128
129 void down_read_non_owner(struct rw_semaphore *sem)
130 {
131         might_sleep();
132
133         __down_read(sem);
134 }
135
136 EXPORT_SYMBOL(down_read_non_owner);
137
138 void 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
146 EXPORT_SYMBOL(down_write_nested);
147
148 void up_read_non_owner(struct rw_semaphore *sem)
149 {
150         __up_read(sem);
151 }
152
153 EXPORT_SYMBOL(up_read_non_owner);
154
155 #endif
156
157