[mirror_ubuntu-artful-kernel.git] / lib / llist.c

/*
 * Lock-less NULL terminated single linked list
 *
 * The basic atomic operation of this list is cmpxchg on long.  On
 * architectures that don't have NMI-safe cmpxchg implementation, the
 * list can NOT be used in NMI handler.  So code uses the list in NMI
 * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
 *
 * Copyright 2010,2011 Intel Corp.
 *   Author: Huang Ying <ying.huang@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/llist.h>

#include <asm/system.h>

/**
 * llist_add_batch - add several linked entries in batch
 * @new_first:	first entry in batch to be added
 * @new_last:	last entry in batch to be added
 * @head:	the head for your lock-less list
 */
void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
		     struct llist_head *head)
{
	struct llist_node *entry, *old_entry;

#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
	BUG_ON(in_nmi());
#endif

	entry = head->first;
	do {
		old_entry = entry;
		new_last->next = entry;
		cpu_relax();
	} while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
}
EXPORT_SYMBOL_GPL(llist_add_batch);

/**
 * llist_del_first - delete the first entry of lock-less list
 * @head:	the head for your lock-less list
 *
 * If list is empty, return NULL, otherwise, return the first entry
 * deleted, this is the newest added one.
 *
 * Only one llist_del_first user can be used simultaneously with
 * multiple llist_add users without lock.  Because otherwise
 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
 * llist_add) sequence in another user may change @head->first->next,
 * but keep @head->first.  If multiple consumers are needed, please
 * use llist_del_all or use lock between consumers.
 */
struct llist_node *llist_del_first(struct llist_head *head)
{
	struct llist_node *entry, *old_entry, *next;

#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
	BUG_ON(in_nmi());
#endif

	entry = head->first;
	do {
		if (entry == NULL)
			return NULL;
		old_entry = entry;
		next = entry->next;
		cpu_relax();
	} while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);

	return entry;
}
EXPORT_SYMBOL_GPL(llist_del_first);
Commit	Line	Data
f49f23ab HY	1	/*
	2	* Lock-less NULL terminated single linked list
	3	*
	4	* The basic atomic operation of this list is cmpxchg on long. On
	5	* architectures that don't have NMI-safe cmpxchg implementation, the
	6	* list can NOT be used in NMI handler. So code uses the list in NMI
	7	* handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
	8	*
	9	* Copyright 2010,2011 Intel Corp.
	10	* Author: Huang Ying <ying.huang@intel.com>
	11	*
	12	* This program is free software; you can redistribute it and/or
	13	* modify it under the terms of the GNU General Public License version
	14	* 2 as published by the Free Software Foundation;
	15	*
	16	* This program is distributed in the hope that it will be useful,
	17	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	19	* GNU General Public License for more details.
	20	*
	21	* You should have received a copy of the GNU General Public License
	22	* along with this program; if not, write to the Free Software
	23	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	24	*/
	25	#include <linux/kernel.h>
	26	#include <linux/module.h>
	27	#include <linux/interrupt.h>
	28	#include <linux/llist.h>
	29
	30	#include <asm/system.h>
	31
f49f23ab HY	32	/**
	33	* llist_add_batch - add several linked entries in batch
	34	* @new_first: first entry in batch to be added
	35	* @new_last: last entry in batch to be added
	36	* @head: the head for your lock-less list
	37	*/
	38	void llist_add_batch(struct llist_node new_first, struct llist_node new_last,
	39	struct llist_head *head)
	40	{
	41	struct llist_node entry, old_entry;
	42
	43	#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
	44	BUG_ON(in_nmi());
	45	#endif
	46
	47	entry = head->first;
	48	do {
	49	old_entry = entry;
	50	new_last->next = entry;
	51	cpu_relax();
	52	} while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
	53	}
	54	EXPORT_SYMBOL_GPL(llist_add_batch);
	55
	56	/**
	57	* llist_del_first - delete the first entry of lock-less list
	58	* @head: the head for your lock-less list
	59	*
	60	* If list is empty, return NULL, otherwise, return the first entry
	61	* deleted, this is the newest added one.
	62	*
	63	* Only one llist_del_first user can be used simultaneously with
	64	* multiple llist_add users without lock. Because otherwise
	65	* llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
	66	* llist_add) sequence in another user may change @head->first->next,
	67	* but keep @head->first. If multiple consumers are needed, please
	68	* use llist_del_all or use lock between consumers.
	69	*/
	70	struct llist_node llist_del_first(struct llist_head head)
	71	{
	72	struct llist_node entry, old_entry, *next;
	73
	74	#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
	75	BUG_ON(in_nmi());
	76	#endif
	77
	78	entry = head->first;
	79	do {
	80	if (entry == NULL)
	81	return NULL;
	82	old_entry = entry;
	83	next = entry->next;
	84	cpu_relax();
	85	} while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);
	86
	87	return entry;
	88	}
	89	EXPORT_SYMBOL_GPL(llist_del_first);