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/types.h>
19 #include <linux/slab.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.
53 * Subtract @count from the refcount, and if 0, call release().
54 * Return 1 if the object was removed, otherwise return 0. Beware, if this
55 * function returns 0, you still can not count on the kref from remaining in
56 * memory. Only use the return value if you want to see if the kref is now
59 static inline int kref_sub(struct kref *kref, unsigned int count,
60 void (*release)(struct kref *kref))
62 WARN_ON(release == NULL);
63 WARN_ON(release == (void (*)(struct kref *))kfree);
65 if (atomic_sub_and_test((int) count, &kref->refcount)) {
73 * kref_put - decrement refcount for object.
75 * @release: pointer to the function that will clean up the object when the
76 * last reference to the object is released.
77 * This pointer is required, and it is not acceptable to pass kfree
78 * in as this function.
80 * Decrement the refcount, and if 0, call release().
81 * Return 1 if the object was removed, otherwise return 0. Beware, if this
82 * function returns 0, you still can not count on the kref from remaining in
83 * memory. Only use the return value if you want to see if the kref is now
86 static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
88 return kref_sub(kref, 1, release);