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>
26 * kref_init - initialize object.
27 * @kref: object in question.
29 static inline void kref_init(struct kref
*kref
)
31 atomic_set(&kref
->refcount
, 1);
35 * kref_get - increment refcount for object.
38 static inline void kref_get(struct kref
*kref
)
40 WARN_ON(!atomic_read(&kref
->refcount
));
41 atomic_inc(&kref
->refcount
);
45 * kref_sub - subtract a number of refcounts for object.
47 * @count: Number of recounts to subtract.
48 * @release: pointer to the function that will clean up the object when the
49 * last reference to the object is released.
50 * This pointer is required, and it is not acceptable to pass kfree
51 * in as this function. If the caller does pass kfree to this
52 * function, you will be publicly mocked mercilessly by the kref
53 * maintainer, and anyone else who happens to notice it. You have
56 * Subtract @count from the refcount, and if 0, call release().
57 * Return 1 if the object was removed, otherwise return 0. Beware, if this
58 * function returns 0, you still can not count on the kref from remaining in
59 * memory. Only use the return value if you want to see if the kref is now
62 static inline int kref_sub(struct kref
*kref
, unsigned int count
,
63 void (*release
)(struct kref
*kref
))
65 WARN_ON(release
== NULL
);
67 if (atomic_sub_and_test((int) count
, &kref
->refcount
)) {
75 * kref_put - decrement refcount for object.
77 * @release: pointer to the function that will clean up the object when the
78 * last reference to the object is released.
79 * This pointer is required, and it is not acceptable to pass kfree
80 * in as this function. If the caller does pass kfree to this
81 * function, you will be publicly mocked mercilessly by the kref
82 * maintainer, and anyone else who happens to notice it. You have
85 * Decrement the refcount, and if 0, call release().
86 * Return 1 if the object was removed, otherwise return 0. Beware, if this
87 * function returns 0, you still can not count on the kref from remaining in
88 * memory. Only use the return value if you want to see if the kref is now
91 static inline int kref_put(struct kref
*kref
, void (*release
)(struct kref
*kref
))
93 return kref_sub(kref
, 1, release
);