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git.proxmox.com Git - mirror_ubuntu-kernels.git/blob - include/linux/kref.h
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);
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
);
43 smp_mb__after_atomic_inc();
47 * kref_put - decrement refcount for object.
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.
54 * Decrement the refcount, and if 0, call release().
55 * Return 1 if the object was removed, otherwise return 0. Beware, if this
56 * function returns 0, you still can not count on the kref from remaining in
57 * memory. Only use the return value if you want to see if the kref is now
60 static inline int kref_put(struct kref
*kref
, void (*release
)(struct kref
*kref
))
62 WARN_ON(release
== NULL
);
63 WARN_ON(release
== (void (*)(struct kref
*))kfree
);
65 if (atomic_dec_and_test(&kref
->refcount
)) {
74 * kref_sub - subtract a number of refcounts for object.
76 * @count: Number of recounts to subtract.
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.
82 * Subtract @count from the refcount, and if 0, call release().
83 * Return 1 if the object was removed, otherwise return 0. Beware, if this
84 * function returns 0, you still can not count on the kref from remaining in
85 * memory. Only use the return value if you want to see if the kref is now
88 static inline int kref_sub(struct kref
*kref
, unsigned int count
,
89 void (*release
)(struct kref
*kref
))
91 WARN_ON(release
== NULL
);
92 WARN_ON(release
== (void (*)(struct kref
*))kfree
);
94 if (atomic_sub_and_test((int) count
, &kref
->refcount
)) {
100 #endif /* _KREF_H_ */