share/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 //#include "<kernelcompat.h>"
  15 #include <kref.h>
  16 //ust// #include <linux/module.h>
  17 #include "usterr.h"
  18 #include "compiler.h"
  19
  20 /**
  21  * kref_set - initialize object and set refcount to requested number.
  22  * @kref: object in question.
  23  * @num: initial reference counter
  24  */
  25 void kref_set(struct kref *kref, int num)
  26 {
  27         atomic_set(&kref->refcount, num);
  28         smp_mb();
  29 }
  30
  31 /**
  32  * kref_init - initialize object.
  33  * @kref: object in question.
  34  */
  35 void kref_init(struct kref *kref)
  36 {
  37         kref_set(kref, 1);
  38 }
  39
  40 /**
  41  * kref_get - increment refcount for object.
  42  * @kref: object.
  43  */
  44 void kref_get(struct kref *kref)
  45 {
  46         WARN_ON(!atomic_read(&kref->refcount));
  47         atomic_inc(&kref->refcount);
  48         smp_mb__after_atomic_inc();
  49 }
  50
  51 /**
  52  * kref_put - decrement refcount for object.
  53  * @kref: 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.
  58  *
  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
  63  * gone, not present.
  64  */
  65 int kref_put(struct kref *kref, void (*release)(struct kref *kref))
  66 {
  67         WARN_ON(release == NULL);
  68 //ust// WARN_ON(release == (void (*)(struct kref *))kfree);
  69
  70         if (atomic_dec_and_test(&kref->refcount)) {
  71                 release(kref);
  72                 return 1;
  73         }
  74         return 0;
  75 }
  76
  77 //ust// EXPORT_SYMBOL(kref_set);
  78 //ust// EXPORT_SYMBOL(kref_init);
  79 //ust// EXPORT_SYMBOL(kref_get);
  80 //ust// EXPORT_SYMBOL(kref_put);