| 1 | |
| 2 | * kref.c - library routines for handling generic reference counted objects
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| 3 | *
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| 4 | * Copyright (C) 2004 Greg Kroah-Hartman <[email protected]>
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| 5 | * Copyright (C) 2004 IBM Corp.
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| 6 | *
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| 7 | * based on lib/kobject.c which was:
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| 8 | * Copyright (C) 2002-2003 Patrick Mochel <[email protected]>
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| 9 | *
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| 10 | * This file is released under the GPLv2.
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| 11 | *
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| 12 |
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| 13 |
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| 14 | #include <linux/kref.h>
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| 15 | #include <linux/module.h>
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| 16 |
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| 17 | |
| 18 | * kref_init - initialize object.
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| 19 | * @kref: object in question.
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| 20 |
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| 21 | void kref_init(struct kref *kref)
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| 22 | {
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| 23 | atomic_set(&kref->refcount,1);
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| 24 | smp_mb();
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| 25 | }
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| 26 |
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| 27 | |
| 28 | * kref_get - increment refcount for object.
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| 29 | * @kref: object.
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| 30 |
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| 31 | void kref_get(struct kref *kref)
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| 32 | {
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| 33 | WARN_ON(!atomic_read(&kref->refcount));
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| 34 | atomic_inc(&kref->refcount);
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| 35 | smp_mb__after_atomic_inc();
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| 36 | }
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| 37 |
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| 38 | |
| 39 | * kref_put - decrement refcount for object.
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| 40 | * @kref: object.
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| 41 | * @release: pointer to the function that will clean up the object when the
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| 42 | * last reference to the object is released.
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| 43 | * This pointer is required, and it is not acceptable to pass kfree
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| 44 | * in as this function.
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| 45 | *
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| 46 | * Decrement the refcount, and if 0, call release().
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| 47 | * Return 1 if the object was removed, otherwise return 0. Beware, if this
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| 48 | * function returns 0, you still can not count on the kref from remaining in
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| 49 | * memory. Only use the return value if you want to see if the kref is now
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| 50 | * gone, not present.
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| 51 |
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| 52 | int kref_put(struct kref *kref, void (*release)(struct kref *kref))
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| 53 | {
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| 54 | WARN_ON(release == NULL);
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| 55 | WARN_ON(release == (void (*)(struct kref *))kfree);
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| 56 |
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| 57 | if (atomic_dec_and_test(&kref->refcount)) {
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| 58 | release(kref);
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| 59 | return 1;
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| 60 | }
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| 61 | return 0;
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| 62 | }
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| 63 |
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| 64 | EXPORT_SYMBOL(kref_init);
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| 65 | EXPORT_SYMBOL(kref_get);
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| 66 | EXPORT_SYMBOL(kref_put);
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