| /* kernel/rwsem.c: R/W semaphores, public implementation |
| * |
| * Written by David Howells (dhowells@redhat.com). |
| * Derived from asm-i386/semaphore.h |
| */ |
| |
| #include <linux/types.h> |
| #include <linux/kernel.h> |
| #include <linux/sched.h> |
| #include <linux/export.h> |
| #include <linux/rwsem.h> |
| #include <linux/atomic.h> |
| |
| #include "rwsem.h" |
| |
| /* |
| * lock for reading |
| */ |
| void __sched down_read(struct rw_semaphore *sem) |
| { |
| might_sleep(); |
| rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); |
| |
| LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
| } |
| |
| EXPORT_SYMBOL(down_read); |
| |
| /* |
| * trylock for reading -- returns 1 if successful, 0 if contention |
| */ |
| int down_read_trylock(struct rw_semaphore *sem) |
| { |
| int ret = __down_read_trylock(sem); |
| |
| if (ret == 1) |
| rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); |
| return ret; |
| } |
| |
| EXPORT_SYMBOL(down_read_trylock); |
| |
| /* |
| * lock for writing |
| */ |
| void __sched down_write(struct rw_semaphore *sem) |
| { |
| might_sleep(); |
| rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); |
| |
| LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
| rwsem_set_owner(sem); |
| } |
| |
| EXPORT_SYMBOL(down_write); |
| |
| /* |
| * lock for writing |
| */ |
| int __sched down_write_killable(struct rw_semaphore *sem) |
| { |
| might_sleep(); |
| rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); |
| |
| if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) { |
| rwsem_release(&sem->dep_map, 1, _RET_IP_); |
| return -EINTR; |
| } |
| |
| rwsem_set_owner(sem); |
| return 0; |
| } |
| |
| EXPORT_SYMBOL(down_write_killable); |
| |
| /* |
| * trylock for writing -- returns 1 if successful, 0 if contention |
| */ |
| int down_write_trylock(struct rw_semaphore *sem) |
| { |
| int ret = __down_write_trylock(sem); |
| |
| if (ret == 1) { |
| rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); |
| rwsem_set_owner(sem); |
| } |
| |
| return ret; |
| } |
| |
| EXPORT_SYMBOL(down_write_trylock); |
| |
| /* |
| * release a read lock |
| */ |
| void up_read(struct rw_semaphore *sem) |
| { |
| rwsem_release(&sem->dep_map, 1, _RET_IP_); |
| |
| __up_read(sem); |
| } |
| |
| EXPORT_SYMBOL(up_read); |
| |
| /* |
| * release a write lock |
| */ |
| void up_write(struct rw_semaphore *sem) |
| { |
| rwsem_release(&sem->dep_map, 1, _RET_IP_); |
| |
| rwsem_clear_owner(sem); |
| __up_write(sem); |
| } |
| |
| EXPORT_SYMBOL(up_write); |
| |
| /* |
| * downgrade write lock to read lock |
| */ |
| void downgrade_write(struct rw_semaphore *sem) |
| { |
| /* |
| * lockdep: a downgraded write will live on as a write |
| * dependency. |
| */ |
| rwsem_clear_owner(sem); |
| __downgrade_write(sem); |
| } |
| |
| EXPORT_SYMBOL(downgrade_write); |
| |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| |
| void down_read_nested(struct rw_semaphore *sem, int subclass) |
| { |
| might_sleep(); |
| rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); |
| |
| LOCK_CONTENDED(sem, __down_read_trylock, __down_read); |
| } |
| |
| EXPORT_SYMBOL(down_read_nested); |
| |
| void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest) |
| { |
| might_sleep(); |
| rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_); |
| |
| LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
| rwsem_set_owner(sem); |
| } |
| |
| EXPORT_SYMBOL(_down_write_nest_lock); |
| |
| void down_read_non_owner(struct rw_semaphore *sem) |
| { |
| might_sleep(); |
| |
| __down_read(sem); |
| } |
| |
| EXPORT_SYMBOL(down_read_non_owner); |
| |
| void down_write_nested(struct rw_semaphore *sem, int subclass) |
| { |
| might_sleep(); |
| rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); |
| |
| LOCK_CONTENDED(sem, __down_write_trylock, __down_write); |
| rwsem_set_owner(sem); |
| } |
| |
| EXPORT_SYMBOL(down_write_nested); |
| |
| int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass) |
| { |
| might_sleep(); |
| rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); |
| |
| if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) { |
| rwsem_release(&sem->dep_map, 1, _RET_IP_); |
| return -EINTR; |
| } |
| |
| rwsem_set_owner(sem); |
| return 0; |
| } |
| |
| EXPORT_SYMBOL(down_write_killable_nested); |
| |
| void up_read_non_owner(struct rw_semaphore *sem) |
| { |
| __up_read(sem); |
| } |
| |
| EXPORT_SYMBOL(up_read_non_owner); |
| |
| #endif |
| |
| |