* kref_set - initialize object and set refcount to requested number.
* @kref: object in question.
/**
* kref_init - initialize object.
* @kref: object in question.
*/
void kref_init(struct kref *kref)
{
/* 初始值是 1 而不是 0 */
kref_set(kref, 1);
}
/**
* kref_get - increment refcount for object.
* @kref: object.
*/
void kref_get(struct kref *kref)
{
/* 增加引用计数 */
WARN_ON(!atomic_read(&kref->refcount));
atomic_inc(&kref->refcount);
smp_mb__after_atomic_inc();
}
/**
* kref_put - decrement refcount for object.
* @kref: object.
* @release: pointer to the function that will clean up the object when the
* last reference to the object is released.
* This pointer is required, and it is not acceptable to pass kfree
* in as this function.
*
* Decrement the refcount, and if 0, call release().
* Return 1 if the object was removed, otherwise return 0. Beware, if this
* function returns 0, you still can not count on the kref from remaining in
* memory. Only use the return value if you want to see if the kref is now
* gone, not present.
*/
int kref_put(struct kref *kref, void (*release)(struct kref *kref))
{
WARN_ON(release == NULL);
WARN_ON(release == (void (*)(struct kref *))kfree);
/* 引用计数减1， 如果为0， 则执行释放函数release */
if (atomic_dec_and_test(&kref->refcount)) {
release(kref);
return 1;
}
return 0;
}
