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>
13 #include <linux/atomic.h>
18 void __sched down_read(struct rw_semaphore *sem)
21 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
23 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
26 EXPORT_SYMBOL(down_read);
29 * trylock for reading -- returns 1 if successful, 0 if contention
31 int down_read_trylock(struct rw_semaphore *sem)
33 int ret = __down_read_trylock(sem);
36 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
40 EXPORT_SYMBOL(down_read_trylock);
45 void __sched down_write(struct rw_semaphore *sem)
48 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
50 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
53 EXPORT_SYMBOL(down_write);
56 * trylock for writing -- returns 1 if successful, 0 if contention
58 int down_write_trylock(struct rw_semaphore *sem)
60 int ret = __down_write_trylock(sem);
63 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
67 EXPORT_SYMBOL(down_write_trylock);
72 void up_read(struct rw_semaphore *sem)
74 rwsem_release(&sem->dep_map, 1, _RET_IP_);
79 EXPORT_SYMBOL(up_read);
82 * release a write lock
84 void up_write(struct rw_semaphore *sem)
86 rwsem_release(&sem->dep_map, 1, _RET_IP_);
91 EXPORT_SYMBOL(up_write);
94 * downgrade write lock to read lock
96 void downgrade_write(struct rw_semaphore *sem)
99 * lockdep: a downgraded write will live on as a write
102 __downgrade_write(sem);
105 EXPORT_SYMBOL(downgrade_write);
107 #ifdef CONFIG_DEBUG_LOCK_ALLOC
109 void down_read_nested(struct rw_semaphore *sem, int subclass)
112 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
114 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
117 EXPORT_SYMBOL(down_read_nested);
119 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
122 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
124 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
127 EXPORT_SYMBOL(_down_write_nest_lock);
129 void down_read_non_owner(struct rw_semaphore *sem)
136 EXPORT_SYMBOL(down_read_non_owner);
138 void down_write_nested(struct rw_semaphore *sem, int subclass)
141 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
143 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
146 EXPORT_SYMBOL(down_write_nested);
148 void up_read_non_owner(struct rw_semaphore *sem)
153 EXPORT_SYMBOL(up_read_non_owner);