[linux.git] / lib / kref.c

/*
 * kref.c - library routines for handling generic reference counted objects
 *
 * Copyright (C) 2004 Greg Kroah-Hartman <[email protected]>
 * Copyright (C) 2004 IBM Corp.
 *
 * based on lib/kobject.c which was:
 * Copyright (C) 2002-2003 Patrick Mochel <[email protected]>
 *
 * This file is released under the GPLv2.
 *
 */

#include <linux/kref.h>
#include <linux/module.h>
#include <linux/slab.h>

/**
 * kref_init - initialize object.
 * @kref: object in question.
 */
void kref_init(struct kref *kref)
{
	atomic_set(&kref->refcount, 1);
	smp_mb();
}

/**
 * kref_get - increment refcount for object.
 * @kref: object.
 */
void kref_get(struct kref *kref)
{
	WARN_ON(!atomic_read(&kref->refcount));
	atomic_inc(&kref->refcount);
	smp_mb__after_atomic_inc();
}

/**
 * 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 (atomic_dec_and_test(&kref->refcount)) {
		release(kref);
		return 1;
	}
	return 0;
}


/**
 * kref_sub - subtract a number of refcounts for object.
 * @kref: object.
 * @count: Number of recounts to subtract.
 * @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.
 *
 * Subtract @count from 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_sub(struct kref *kref, unsigned int count,
	     void (*release)(struct kref *kref))
{
	WARN_ON(release == NULL);
	WARN_ON(release == (void (*)(struct kref *))kfree);

	if (atomic_sub_and_test((int) count, &kref->refcount)) {
		release(kref);
		return 1;
	}
	return 0;
}

EXPORT_SYMBOL(kref_init);
EXPORT_SYMBOL(kref_get);
EXPORT_SYMBOL(kref_put);
EXPORT_SYMBOL(kref_sub);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* kref.c - library routines for handling generic reference counted objects
	3	*
	4	* Copyright (C) 2004 Greg Kroah-Hartman <[email protected]>
	5	* Copyright (C) 2004 IBM Corp.
	6	*
	7	* based on lib/kobject.c which was:
	8	* Copyright (C) 2002-2003 Patrick Mochel <[email protected]>
	9	*
	10	* This file is released under the GPLv2.
	11	*
	12	*/
	13
	14	#include <linux/kref.h>
	15	#include <linux/module.h>
5a0e3ad6	16	#include <linux/slab.h>
1da177e4 LT	17
	18	/**
	19	* kref_init - initialize object.
	20	* @kref: object in question.
	21	*/
	22	void kref_init(struct kref *kref)
	23	{
db1afffa N	24	atomic_set(&kref->refcount, 1);
db1afffa N	25	smp_mb();
1da177e4 LT	26	}
	27
	28	/**
	29	* kref_get - increment refcount for object.
	30	* @kref: object.
	31	*/
	32	void kref_get(struct kref *kref)
	33	{
	34	WARN_ON(!atomic_read(&kref->refcount));
	35	atomic_inc(&kref->refcount);
1b0b3b99	36	smp_mb__after_atomic_inc();
1da177e4 LT	37	}
	38
	39	/**
	40	* kref_put - decrement refcount for object.
	41	* @kref: object.
	42	* @release: pointer to the function that will clean up the object when the
	43	* last reference to the object is released.
	44	* This pointer is required, and it is not acceptable to pass kfree
	45	* in as this function.
	46	*
	47	* Decrement the refcount, and if 0, call release().
	48	* Return 1 if the object was removed, otherwise return 0. Beware, if this
	49	* function returns 0, you still can not count on the kref from remaining in
	50	* memory. Only use the return value if you want to see if the kref is now
	51	* gone, not present.
	52	*/
	53	int kref_put(struct kref kref, void (release)(struct kref *kref))
	54	{
	55	WARN_ON(release == NULL);
	56	WARN_ON(release == (void ()(struct kref ))kfree);
	57
f334b60b	58	if (atomic_dec_and_test(&kref->refcount)) {
1da177e4 LT	59	release(kref);
	60	return 1;
	61	}
	62	return 0;
	63	}
	64
ecf7ace9 TH	65
	66	/**
	67	* kref_sub - subtract a number of refcounts for object.
	68	* @kref: object.
	69	* @count: Number of recounts to subtract.
	70	* @release: pointer to the function that will clean up the object when the
	71	* last reference to the object is released.
	72	* This pointer is required, and it is not acceptable to pass kfree
	73	* in as this function.
	74	*
	75	* Subtract @count from the refcount, and if 0, call release().
	76	* Return 1 if the object was removed, otherwise return 0. Beware, if this
	77	* function returns 0, you still can not count on the kref from remaining in
	78	* memory. Only use the return value if you want to see if the kref is now
	79	* gone, not present.
	80	*/
	81	int kref_sub(struct kref *kref, unsigned int count,
	82	void (release)(struct kref kref))
	83	{
	84	WARN_ON(release == NULL);
	85	WARN_ON(release == (void ()(struct kref ))kfree);
	86
	87	if (atomic_sub_and_test((int) count, &kref->refcount)) {
	88	release(kref);
	89	return 1;
	90	}
	91	return 0;
	92	}
	93
1da177e4 LT	94	EXPORT_SYMBOL(kref_init);
	95	EXPORT_SYMBOL(kref_get);
	96	EXPORT_SYMBOL(kref_put);
ecf7ace9	97	EXPORT_SYMBOL(kref_sub);