2 * kref.c - 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 lib/kobject.c which was:
8 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
10 * This file is released under the GPLv2.
14 #include <linux/kref.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
19 * kref_init - initialize object.
20 * @kref: object in question.
22 void kref_init(struct kref
*kref
)
24 atomic_set(&kref
->refcount
, 1);
29 * kref_get - increment refcount for object.
32 void kref_get(struct kref
*kref
)
34 WARN_ON(!atomic_read(&kref
->refcount
));
35 atomic_inc(&kref
->refcount
);
36 smp_mb__after_atomic_inc();
40 * kref_test_and_get - increment refcount for object only if refcount is not
44 * Return non-zero if the refcount was incremented, 0 otherwise
46 int kref_test_and_get(struct kref
*kref
)
48 return atomic_inc_not_zero(&kref
->refcount
);
52 * kref_put - decrement refcount for object.
54 * @release: pointer to the function that will clean up the object when the
55 * last reference to the object is released.
56 * This pointer is required, and it is not acceptable to pass kfree
57 * in as this function.
59 * Decrement the refcount, and if 0, call release().
60 * Return 1 if the object was removed, otherwise return 0. Beware, if this
61 * function returns 0, you still can not count on the kref from remaining in
62 * memory. Only use the return value if you want to see if the kref is now
65 int kref_put(struct kref
*kref
, void (*release
)(struct kref
*kref
))
67 WARN_ON(release
== NULL
);
68 WARN_ON(release
== (void (*)(struct kref
*))kfree
);
70 if (atomic_dec_and_test(&kref
->refcount
)) {
77 EXPORT_SYMBOL(kref_init
);
78 EXPORT_SYMBOL(kref_get
);
79 EXPORT_SYMBOL(kref_put
);