Linux kernel mirror (for testing)
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1/*
2 * kref.c - library routines for handling generic reference counted objects
3 *
4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5 * Copyright (C) 2004 IBM Corp.
6 *
7 * based on lib/kobject.c which was:
8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
9 *
10 * This file is released under the GPLv2.
11 *
12 */
13
14#include <linux/kref.h>
15#include <linux/module.h>
16
17/**
18 * kref_init - initialize object.
19 * @kref: object in question.
20 */
21void kref_init(struct kref *kref)
22{
23 atomic_set(&kref->refcount,1);
24}
25
26/**
27 * kref_get - increment refcount for object.
28 * @kref: object.
29 */
30void kref_get(struct kref *kref)
31{
32 WARN_ON(!atomic_read(&kref->refcount));
33 atomic_inc(&kref->refcount);
34}
35
36/**
37 * kref_put - decrement refcount for object.
38 * @kref: object.
39 * @release: pointer to the function that will clean up the object when the
40 * last reference to the object is released.
41 * This pointer is required, and it is not acceptable to pass kfree
42 * in as this function.
43 *
44 * Decrement the refcount, and if 0, call release().
45 * Return 1 if the object was removed, otherwise return 0. Beware, if this
46 * function returns 0, you still can not count on the kref from remaining in
47 * memory. Only use the return value if you want to see if the kref is now
48 * gone, not present.
49 */
50int kref_put(struct kref *kref, void (*release)(struct kref *kref))
51{
52 WARN_ON(release == NULL);
53 WARN_ON(release == (void (*)(struct kref *))kfree);
54
55 if (atomic_dec_and_test(&kref->refcount)) {
56 release(kref);
57 return 1;
58 }
59 return 0;
60}
61
62EXPORT_SYMBOL(kref_init);
63EXPORT_SYMBOL(kref_get);
64EXPORT_SYMBOL(kref_put);