1 /* kernel/rwsem.c: R/W semaphores, public implementation
3 * Written by David Howells (dhowells@redhat.com).
4 * Derived from asm-i386/semaphore.h
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>
19 void __sched down_read(struct rw_semaphore *sem)
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);
37 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
41 EXPORT_SYMBOL(down_read_trylock);
46 void __sched down_write(struct rw_semaphore *sem)
49 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
51 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
55 EXPORT_SYMBOL(down_write);
60 int __sched down_write_killable(struct rw_semaphore *sem)
63 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
65 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
66 rwsem_release(&sem->dep_map, 1, _RET_IP_);
74 EXPORT_SYMBOL(down_write_killable);
77 * trylock for writing -- returns 1 if successful, 0 if contention
79 int down_write_trylock(struct rw_semaphore *sem)
81 int ret = __down_write_trylock(sem);
84 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
91 EXPORT_SYMBOL(down_write_trylock);
96 void up_read(struct rw_semaphore *sem)
98 rwsem_release(&sem->dep_map, 1, _RET_IP_);
103 EXPORT_SYMBOL(up_read);
106 * release a write lock
108 void up_write(struct rw_semaphore *sem)
110 rwsem_release(&sem->dep_map, 1, _RET_IP_);
112 rwsem_clear_owner(sem);
116 EXPORT_SYMBOL(up_write);
119 * downgrade write lock to read lock
121 void downgrade_write(struct rw_semaphore *sem)
124 * lockdep: a downgraded write will live on as a write
127 rwsem_clear_owner(sem);
128 __downgrade_write(sem);
131 EXPORT_SYMBOL(downgrade_write);
133 #ifdef CONFIG_DEBUG_LOCK_ALLOC
135 void down_read_nested(struct rw_semaphore *sem, int subclass)
138 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
140 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
143 EXPORT_SYMBOL(down_read_nested);
145 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
148 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
150 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
151 rwsem_set_owner(sem);
154 EXPORT_SYMBOL(_down_write_nest_lock);
156 void down_read_non_owner(struct rw_semaphore *sem)
163 EXPORT_SYMBOL(down_read_non_owner);
165 void down_write_nested(struct rw_semaphore *sem, int subclass)
168 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
170 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
171 rwsem_set_owner(sem);
174 EXPORT_SYMBOL(down_write_nested);
176 void up_read_non_owner(struct rw_semaphore *sem)
181 EXPORT_SYMBOL(up_read_non_owner);