blob: 4a467faf1367bb031d49eb136ac16de0551a1629 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Eric Dumazet8b5536b2006-01-30 06:19:35 +010055 /*
56 * if current count is one, we are the last user and can release object
57 * right now, avoiding an atomic operation on 'refcount'
58 */
59 if ((atomic_read(&kref->refcount) == 1) ||
60 (atomic_dec_and_test(&kref->refcount))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 release(kref);
62 return 1;
63 }
64 return 0;
65}
66
67EXPORT_SYMBOL(kref_init);
68EXPORT_SYMBOL(kref_get);
69EXPORT_SYMBOL(kref_put);