Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1/*
2 * kref.h - 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 kobject.h which was:
8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
9 * Copyright (C) 2002-2003 Open Source Development Labs
10 *
11 * This file is released under the GPLv2.
12 *
13 */
14
15#ifndef _KREF_H_
16#define _KREF_H_
17
18#include <linux/bug.h>
19#include <linux/atomic.h>
20#include <linux/kernel.h>
21
22struct kref {
23 atomic_t refcount;
24};
25
26/**
27 * kref_init - initialize object.
28 * @kref: object in question.
29 */
30static inline void kref_init(struct kref *kref)
31{
32 atomic_set(&kref->refcount, 1);
33}
34
35/**
36 * kref_get - increment refcount for object.
37 * @kref: object.
38 */
39static inline void kref_get(struct kref *kref)
40{
41 WARN_ON(!atomic_read(&kref->refcount));
42 atomic_inc(&kref->refcount);
43}
44
45/**
46 * kref_sub - subtract a number of refcounts for object.
47 * @kref: object.
48 * @count: Number of recounts to subtract.
49 * @release: pointer to the function that will clean up the object when the
50 * last reference to the object is released.
51 * This pointer is required, and it is not acceptable to pass kfree
52 * in as this function. If the caller does pass kfree to this
53 * function, you will be publicly mocked mercilessly by the kref
54 * maintainer, and anyone else who happens to notice it. You have
55 * been warned.
56 *
57 * Subtract @count from 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 */
63static inline int kref_sub(struct kref *kref, unsigned int count,
64 void (*release)(struct kref *kref))
65{
66 WARN_ON(release == NULL);
67
68 if (atomic_sub_and_test((int) count, &kref->refcount)) {
69 release(kref);
70 return 1;
71 }
72 return 0;
73}
74
75/**
76 * kref_put - decrement refcount for object.
77 * @kref: object.
78 * @release: pointer to the function that will clean up the object when the
79 * last reference to the object is released.
80 * This pointer is required, and it is not acceptable to pass kfree
81 * in as this function. If the caller does pass kfree to this
82 * function, you will be publicly mocked mercilessly by the kref
83 * maintainer, and anyone else who happens to notice it. You have
84 * been warned.
85 *
86 * Decrement the refcount, and if 0, call release().
87 * Return 1 if the object was removed, otherwise return 0. Beware, if this
88 * function returns 0, you still can not count on the kref from remaining in
89 * memory. Only use the return value if you want to see if the kref is now
90 * gone, not present.
91 */
92static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
93{
94 return kref_sub(kref, 1, release);
95}
96#endif /* _KREF_H_ */