lib/kref.c

   1 /*
   2  * kref.c - library routines for handling generic reference counted objects
   3  *
   4  * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   5  * Copyright (C) 2004 IBM Corp.
   6  *
   7  * based on lib/kobject.c which was:
   8  * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
   9  *
  10  * This file is released under the GPLv2.
  11  *
  12  */
  13
  14 /* #define DEBUG */
  15
  16 #include <linux/kref.h>
  17 #include <linux/module.h>
  18
  19 /**
  20  * kref_init - initialize object.
  21  * @kref: object in question.
  22  * @release: pointer to a function that will clean up the object
  23  *           when the last reference to the object is released.
  24  *           This pointer is required.
  25  */
  26 void kref_init(struct kref *kref, void (*release)(struct kref *kref))
  27 {
  28         WARN_ON(release == NULL);
  29         atomic_set(&kref->refcount,1);
  30         kref->release = release;
  31 }
  32
  33 /**
  34  * kref_get - increment refcount for object.
  35  * @kref: object.
  36  */
  37 struct kref *kref_get(struct kref *kref)
  38 {
  39         WARN_ON(!atomic_read(&kref->refcount));
  40         atomic_inc(&kref->refcount);
  41         return kref;
  42 }
  43
  44 /**
  45  * kref_put - decrement refcount for object.
  46  * @kref: object.
  47  *
  48  * Decrement the refcount, and if 0, call kref->release().
  49  */
  50 void kref_put(struct kref *kref)
  51 {
  52         if (atomic_dec_and_test(&kref->refcount)) {
  53                 pr_debug("kref cleaning up\n");
  54                 kref->release(kref);
  55         }
  56 }
  57
  58 EXPORT_SYMBOL(kref_init);
  59 EXPORT_SYMBOL(kref_get);
  60 EXPORT_SYMBOL(kref_put);