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/* rwsem.h: R/W semaphores, public interface
*
* Written by David Howells (dhowells@redhat.com).
* Derived from asm-i386/semaphore.h
*/
#ifndef _LINUX_RWSEM_H
#define _LINUX_RWSEM_H
#include <linux/linkage.h>
#define RWSEM_DEBUG 0
#ifdef __KERNEL__
#include <linux/types.h>
#include <linux/kernel.h>
#include <asm/system.h>
#include <asm/atomic.h>
struct rw_semaphore;
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
#include <linux/rwsem-spinlock.h> /* use a generic implementation */
#else
#include <asm/rwsem.h> /* use an arch-specific implementation */
#endif
#ifndef rwsemtrace
#if RWSEM_DEBUG
extern void FASTCALL(rwsemtrace(struct rw_semaphore *sem, const char *str));
#else
#define rwsemtrace(SEM,FMT)
#endif
#endif
/*
* lock for reading
*/
static inline void down_read(struct rw_semaphore *sem)
{
might_sleep();
rwsemtrace(sem,"Entering down_read");
__down_read(sem);
rwsemtrace(sem,"Leaving down_read");
}
/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
static inline int down_read_trylock(struct rw_semaphore *sem)
{
int ret;
rwsemtrace(sem,"Entering down_read_trylock");
ret = __down_read_trylock(sem);
rwsemtrace(sem,"Leaving down_read_trylock");
return ret;
}
/*
* lock for writing
*/
static inline void down_write(struct rw_semaphore *sem)
{
might_sleep();
rwsemtrace(sem,"Entering down_write");
__down_write(sem);
rwsemtrace(sem,"Leaving down_write");
}
/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
static inline int down_write_trylock(struct rw_semaphore *sem)
{
int ret;
rwsemtrace(sem,"Entering down_write_trylock");
ret = __down_write_trylock(sem);
rwsemtrace(sem,"Leaving down_write_trylock");
return ret;
}
/*
* release a read lock
*/
static inline void up_read(struct rw_semaphore *sem)
{
rwsemtrace(sem,"Entering up_read");
__up_read(sem);
rwsemtrace(sem,"Leaving up_read");
}
/*
* release a write lock
*/
static inline void up_write(struct rw_semaphore *sem)
{
rwsemtrace(sem,"Entering up_write");
__up_write(sem);
rwsemtrace(sem,"Leaving up_write");
}
/*
* downgrade write lock to read lock
*/
static inline void downgrade_write(struct rw_semaphore *sem)
{
rwsemtrace(sem,"Entering downgrade_write");
__downgrade_write(sem);
rwsemtrace(sem,"Leaving downgrade_write");
}
#endif /* __KERNEL__ */
#endif /* _LINUX_RWSEM_H */
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