106 lines
1.8 KiB
C
106 lines
1.8 KiB
C
/* kernel/rwsem.c: R/W semaphores, public implementation
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*
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* Written by David Howells (dhowells@redhat.com).
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* Derived from asm-i386/semaphore.h
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/rwsem.h>
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#include <asm/system.h>
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#include <asm/atomic.h>
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/*
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* lock for reading
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*/
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void down_read(struct rw_semaphore *sem)
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{
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might_sleep();
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rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
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__down_read(sem);
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}
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EXPORT_SYMBOL(down_read);
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/*
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* trylock for reading -- returns 1 if successful, 0 if contention
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*/
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int down_read_trylock(struct rw_semaphore *sem)
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{
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int ret = __down_read_trylock(sem);
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if (ret == 1)
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rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
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return ret;
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}
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EXPORT_SYMBOL(down_read_trylock);
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/*
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* lock for writing
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*/
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void down_write(struct rw_semaphore *sem)
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{
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might_sleep();
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rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
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__down_write(sem);
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}
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EXPORT_SYMBOL(down_write);
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/*
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* trylock for writing -- returns 1 if successful, 0 if contention
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*/
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int down_write_trylock(struct rw_semaphore *sem)
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{
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int ret = __down_write_trylock(sem);
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if (ret == 1)
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rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
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return ret;
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}
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EXPORT_SYMBOL(down_write_trylock);
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/*
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* release a read lock
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*/
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void up_read(struct rw_semaphore *sem)
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{
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rwsem_release(&sem->dep_map, 1, _RET_IP_);
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__up_read(sem);
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}
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EXPORT_SYMBOL(up_read);
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/*
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* release a write lock
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*/
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void up_write(struct rw_semaphore *sem)
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{
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rwsem_release(&sem->dep_map, 1, _RET_IP_);
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__up_write(sem);
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}
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EXPORT_SYMBOL(up_write);
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/*
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* downgrade write lock to read lock
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*/
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void downgrade_write(struct rw_semaphore *sem)
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{
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/*
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* lockdep: a downgraded write will live on as a write
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* dependency.
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*/
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__downgrade_write(sem);
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}
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EXPORT_SYMBOL(downgrade_write);
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