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1da177e4 LT |
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> | |
5a0e3ad6 | 16 | #include <linux/slab.h> |
1da177e4 | 17 | |
41ca28ab EP |
18 | /** |
19 | * kref_set - initialize object and set refcount to requested number. | |
20 | * @kref: object in question. | |
21 | * @num: initial reference counter | |
22 | */ | |
23 | void kref_set(struct kref *kref, int num) | |
24 | { | |
25 | atomic_set(&kref->refcount, num); | |
26 | smp_mb(); | |
27 | } | |
28 | ||
1da177e4 LT |
29 | /** |
30 | * kref_init - initialize object. | |
31 | * @kref: object in question. | |
32 | */ | |
33 | void kref_init(struct kref *kref) | |
34 | { | |
41ca28ab | 35 | kref_set(kref, 1); |
1da177e4 LT |
36 | } |
37 | ||
38 | /** | |
39 | * kref_get - increment refcount for object. | |
40 | * @kref: object. | |
41 | */ | |
42 | void kref_get(struct kref *kref) | |
43 | { | |
44 | WARN_ON(!atomic_read(&kref->refcount)); | |
45 | atomic_inc(&kref->refcount); | |
1b0b3b99 | 46 | smp_mb__after_atomic_inc(); |
1da177e4 LT |
47 | } |
48 | ||
49 | /** | |
50 | * kref_put - decrement refcount for object. | |
51 | * @kref: object. | |
52 | * @release: pointer to the function that will clean up the object when the | |
53 | * last reference to the object is released. | |
54 | * This pointer is required, and it is not acceptable to pass kfree | |
55 | * in as this function. | |
56 | * | |
57 | * Decrement the refcount, and if 0, call release(). | |
58 | * Return 1 if the object was removed, otherwise return 0. Beware, if this | |
59 | * function returns 0, you still can not count on the kref from remaining in | |
60 | * memory. Only use the return value if you want to see if the kref is now | |
61 | * gone, not present. | |
62 | */ | |
63 | int kref_put(struct kref *kref, void (*release)(struct kref *kref)) | |
64 | { | |
65 | WARN_ON(release == NULL); | |
66 | WARN_ON(release == (void (*)(struct kref *))kfree); | |
67 | ||
f334b60b | 68 | if (atomic_dec_and_test(&kref->refcount)) { |
1da177e4 LT |
69 | release(kref); |
70 | return 1; | |
71 | } | |
72 | return 0; | |
73 | } | |
74 | ||
41ca28ab | 75 | EXPORT_SYMBOL(kref_set); |
1da177e4 LT |
76 | EXPORT_SYMBOL(kref_init); |
77 | EXPORT_SYMBOL(kref_get); | |
78 | EXPORT_SYMBOL(kref_put); |