*
*/
-/* #define DEBUG */
-
#include <linux/kref.h>
#include <linux/module.h>
/**
* kref_init - initialize object.
* @kref: object in question.
- * @release: pointer to a function that will clean up the object
- * when the last reference to the object is released.
- * This pointer is required.
*/
-void kref_init(struct kref *kref, void (*release)(struct kref *kref))
+void kref_init(struct kref *kref)
{
- WARN_ON(release == NULL);
atomic_set(&kref->refcount,1);
- kref->release = release;
}
/**
* kref_get - increment refcount for object.
* @kref: object.
*/
-struct kref *kref_get(struct kref *kref)
+void kref_get(struct kref *kref)
{
WARN_ON(!atomic_read(&kref->refcount));
atomic_inc(&kref->refcount);
- return kref;
}
/**
* 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 kref->release().
+ * 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.
*/
-void kref_put(struct kref *kref)
+int kref_put(struct kref *kref, void (*release)(struct kref *kref))
{
- if (atomic_dec_and_test(&kref->refcount)) {
- pr_debug("kref cleaning up\n");
- kref->release(kref);
+ WARN_ON(release == NULL);
+ WARN_ON(release == (void (*)(struct kref *))kfree);
+
+ /*
+ * if current count is one, we are the last user and can release object
+ * right now, avoiding an atomic operation on 'refcount'
+ */
+ if ((atomic_read(&kref->refcount) == 1) ||
+ (atomic_dec_and_test(&kref->refcount))) {
+ release(kref);
+ return 1;
}
+ return 0;
}
EXPORT_SYMBOL(kref_init);