/*
   * kref.c - library routines for handling generic reference counted objects
   *
   * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   * Copyright (C) 2004 IBM Corp.
   *
   * based on lib/kobject.c which was:
   * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
   *
   * This file is released under the GPLv2.
   *
   */
  
  #include <linux/kref.h>
  #include <linux/module.h>
  
  /**
   * kref_init - initialize object.
   * @kref: object in question.
   */
  void kref_init(struct kref *kref)
  {
  	atomic_set(&kref->refcount,1);
  }
  
  /**
   * kref_get - increment refcount for object.
   * @kref: object.
   */
  void kref_get(struct kref *kref)
  {
  	WARN_ON(!atomic_read(&kref->refcount));
  	atomic_inc(&kref->refcount);
  }
  
  /**
   * kref_put - decrement refcount for object.
   * @kref: object.
   * @release: pointer to the function that will clean up the object when the
   *	     last reference to the object is released.
   *	     This pointer is required, and it is not acceptable to pass kfree
   *	     in as this function.
   *
   * Decrement the refcount, and if 0, call release().
   * Return 1 if the object was removed, otherwise return 0.  Beware, if this
   * function returns 0, you still can not count on the kref from remaining in
   * memory.  Only use the return value if you want to see if the kref is now
   * gone, not present.
   */
  int kref_put(struct kref *kref, void (*release)(struct kref *kref))
  {
  	WARN_ON(release == NULL);
  	WARN_ON(release == (void (*)(struct kref *))kfree);

  	/*
  	 * if current count is one, we are the last user and can release object
  	 * right now, avoiding an atomic operation on 'refcount'
  	 */
  	if ((atomic_read(&kref->refcount) == 1) ||
  	    (atomic_dec_and_test(&kref->refcount))) {

  		release(kref);
  		return 1;
  	}
  	return 0;
  }
  
  EXPORT_SYMBOL(kref_init);
  EXPORT_SYMBOL(kref_get);
  EXPORT_SYMBOL(kref_put);