2 * kref.h - library routines for handling generic reference counted objects
4 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5 * Copyright (C) 2004 IBM Corp.
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
11 * This file is released under the GPLv2.
18 #include <linux/bug.h>
19 #include <linux/atomic.h>
20 #include <linux/kernel.h>
27 * kref_init - initialize object.
28 * @kref: object in question.
30 static inline void kref_init(struct kref
*kref
)
32 atomic_set(&kref
->refcount
, 1);
36 * kref_get - increment refcount for object.
39 static inline void kref_get(struct kref
*kref
)
41 WARN_ON(!atomic_read(&kref
->refcount
));
42 atomic_inc(&kref
->refcount
);
46 * kref_sub - subtract a number of refcounts for 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
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
63 static inline int kref_sub(struct kref
*kref
, unsigned int count
,
64 void (*release
)(struct kref
*kref
))
66 WARN_ON(release
== NULL
);
68 if (atomic_sub_and_test((int) count
, &kref
->refcount
)) {
76 * kref_put - decrement refcount for 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
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
92 static inline int kref_put(struct kref
*kref
, void (*release
)(struct kref
*kref
))
94 return kref_sub(kref
, 1, release
);
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