Input: implement input filters
[linux/fpc-iii.git] / kernel / rwsem.c
blobcae050b05f5ef91b22547dc88e6b6abc39877018
1 /* kernel/rwsem.c: R/W semaphores, public implementation
3 * Written by David Howells (dhowells@redhat.com).
4 * Derived from asm-i386/semaphore.h
5 */
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>
13 #include <asm/system.h>
14 #include <asm/atomic.h>
17 * lock for reading
19 void __sched down_read(struct rw_semaphore *sem)
21 might_sleep();
22 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
24 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
27 EXPORT_SYMBOL(down_read);
30 * trylock for reading -- returns 1 if successful, 0 if contention
32 int down_read_trylock(struct rw_semaphore *sem)
34 int ret = __down_read_trylock(sem);
36 if (ret == 1)
37 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
38 return ret;
41 EXPORT_SYMBOL(down_read_trylock);
44 * lock for writing
46 void __sched down_write(struct rw_semaphore *sem)
48 might_sleep();
49 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
51 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
54 EXPORT_SYMBOL(down_write);
57 * trylock for writing -- returns 1 if successful, 0 if contention
59 int down_write_trylock(struct rw_semaphore *sem)
61 int ret = __down_write_trylock(sem);
63 if (ret == 1)
64 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
65 return ret;
68 EXPORT_SYMBOL(down_write_trylock);
71 * release a read lock
73 void up_read(struct rw_semaphore *sem)
75 rwsem_release(&sem->dep_map, 1, _RET_IP_);
77 __up_read(sem);
80 EXPORT_SYMBOL(up_read);
83 * release a write lock
85 void up_write(struct rw_semaphore *sem)
87 rwsem_release(&sem->dep_map, 1, _RET_IP_);
89 __up_write(sem);
92 EXPORT_SYMBOL(up_write);
95 * downgrade write lock to read lock
97 void downgrade_write(struct rw_semaphore *sem)
100 * lockdep: a downgraded write will live on as a write
101 * dependency.
103 __downgrade_write(sem);
106 EXPORT_SYMBOL(downgrade_write);
108 #ifdef CONFIG_DEBUG_LOCK_ALLOC
110 void down_read_nested(struct rw_semaphore *sem, int subclass)
112 might_sleep();
113 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
115 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
118 EXPORT_SYMBOL(down_read_nested);
120 void down_read_non_owner(struct rw_semaphore *sem)
122 might_sleep();
124 __down_read(sem);
127 EXPORT_SYMBOL(down_read_non_owner);
129 void down_write_nested(struct rw_semaphore *sem, int subclass)
131 might_sleep();
132 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
134 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
137 EXPORT_SYMBOL(down_write_nested);
139 void up_read_non_owner(struct rw_semaphore *sem)
141 __up_read(sem);
144 EXPORT_SYMBOL(up_read_non_owner);
146 #endif