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/*

 * kref.c - library routines for handling generic reference counted objects

 *

 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>

 * Copyright (C) 2004 IBM Corp.

 *

 * based on lib/kobject.c which was:

 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>

 *

 * This file is released under the GPLv2.

 *

 */

#include <linux/kref.h>

#include <linux/module.h>

/**

 * kref_init - initialize object.

 * @kref: object in question.

 */

void kref_init(struct kref *kref)

{

        atomic_set(&kref->refcount,1);

        smp_mb();

}

/**

 * kref_get - increment refcount for object.

 * @kref: object.

 */

void kref_get(struct kref *kref)

{

        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);

        if (atomic_dec_and_test(&kref->refcount)) {

                release(kref);

                return 1;

        }

        return 0;

}

EXPORT_SYMBOL(kref_init);

EXPORT_SYMBOL(kref_get);

EXPORT_SYMBOL(kref_put);