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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 | #include <linux/slab.h> |
17 | |
18 | /** |
19 | * kref_init - initialize object. |
20 | * @kref: object in question. |
21 | */ |
22 | void kref_init(struct kref *kref) |
23 | { |
24 | atomic_set(&kref->refcount, 1); |
25 | smp_mb(); |
26 | } |
27 | |
28 | /** |
29 | * kref_get - increment refcount for object. |
30 | * @kref: object. |
31 | */ |
32 | void kref_get(struct kref *kref) |
33 | { |
34 | WARN_ON(!atomic_read(&kref->refcount)); |
35 | atomic_inc(&kref->refcount); |
36 | smp_mb__after_atomic_inc(); |
37 | } |
38 | |
39 | /** |
40 | * kref_put - decrement refcount for object. |
41 | * @kref: object. |
42 | * @release: pointer to the function that will clean up the object when the |
43 | * last reference to the object is released. |
44 | * This pointer is required, and it is not acceptable to pass kfree |
45 | * in as this function. |
46 | * |
47 | * Decrement the refcount, and if 0, call release(). |
48 | * Return 1 if the object was removed, otherwise return 0. Beware, if this |
49 | * function returns 0, you still can not count on the kref from remaining in |
50 | * memory. Only use the return value if you want to see if the kref is now |
51 | * gone, not present. |
52 | */ |
53 | int kref_put(struct kref *kref, void (*release)(struct kref *kref)) |
54 | { |
55 | WARN_ON(release == NULL); |
56 | WARN_ON(release == (void (*)(struct kref *))kfree); |
57 | |
58 | if (atomic_dec_and_test(&kref->refcount)) { |
59 | release(kref); |
60 | return 1; |
61 | } |
62 | return 0; |
63 | } |
64 | |
65 | EXPORT_SYMBOL(kref_init); |
66 | EXPORT_SYMBOL(kref_get); |
67 | EXPORT_SYMBOL(kref_put); |
68 |
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