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#ifndef __LINUX_LOCKREF_H
#define __LINUX_LOCKREF_H
/*
* Locked reference counts.
*
* These are different from just plain atomic refcounts in that they
* are atomic with respect to the spinlock that goes with them. In
* particular, there can be implementations that don't actually get
* the spinlock for the common decrement/increment operations, but they
* still have to check that the operation is done semantically as if
* the spinlock had been taken (using a cmpxchg operation that covers
* both the lock and the count word, or using memory transactions, for
* example).
*/
#include <linux/spinlock.h>
struct lockref {
spinlock_t lock;
unsigned int count;
};
/**
* lockref_get - Increments reference count unconditionally
* @lockcnt: pointer to lockref structure
*
* This operation is only valid if you already hold a reference
* to the object, so you know the count cannot be zero.
*/
static inline void lockref_get(struct lockref *lockref)
{
spin_lock(&lockref->lock);
lockref->count++;
spin_unlock(&lockref->lock);
}
/**
* lockref_get_not_zero - Increments count unless the count is 0
* @lockcnt: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count is 0
*/
static inline int lockref_get_not_zero(struct lockref *lockref)
{
int retval = 0;
spin_lock(&lockref->lock);
if (lockref->count) {
lockref->count++;
retval = 1;
}
spin_unlock(&lockref->lock);
return retval;
}
/**
* lockref_get_or_lock - Increments count unless the count is 0
* @lockcnt: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count was zero
* and we got the lock instead.
*/
static inline int lockref_get_or_lock(struct lockref *lockref)
{
spin_lock(&lockref->lock);
if (!lockref->count)
return 0;
lockref->count++;
spin_unlock(&lockref->lock);
return 1;
}
/**
* lockref_put_or_lock - decrements count unless count <= 1 before decrement
* @lockcnt: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
*/
static inline int lockref_put_or_lock(struct lockref *lockref)
{
spin_lock(&lockref->lock);
if (lockref->count <= 1)
return 0;
lockref->count--;
spin_unlock(&lockref->lock);
return 1;
}
#endif /* __LINUX_LOCKREF_H */
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