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Huang Yingf49f23a2011-07-13 13:14:23 +08001/*
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
Ingo Molnar2c302452011-10-04 12:43:11 +02006 * list can NOT be used in NMI handlers. So code that uses the list in
7 * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
Huang Yingf49f23a2011-07-13 13:14:23 +08008 *
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>
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -050026#include <linux/export.h>
Huang Yingf49f23a2011-07-13 13:14:23 +080027#include <linux/interrupt.h>
28#include <linux/llist.h>
29
Huang Yingf49f23a2011-07-13 13:14:23 +080030
31/**
Huang Yingf49f23a2011-07-13 13:14:23 +080032 * llist_add_batch - add several linked entries in batch
33 * @new_first: first entry in batch to be added
34 * @new_last: last entry in batch to be added
35 * @head: the head for your lock-less list
Huang Ying781f7fd2011-09-08 14:00:45 +080036 *
37 * Return whether list is empty before adding.
Huang Yingf49f23a2011-07-13 13:14:23 +080038 */
Huang Ying781f7fd2011-09-08 14:00:45 +080039bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
Huang Yingf49f23a2011-07-13 13:14:23 +080040 struct llist_head *head)
41{
Oleg Nesterovfb4214d2013-07-08 14:24:18 -070042 struct llist_node *first;
Huang Yingf49f23a2011-07-13 13:14:23 +080043
Oleg Nesterovfb4214d2013-07-08 14:24:18 -070044 do {
45 new_last->next = first = ACCESS_ONCE(head->first);
46 } while (cmpxchg(&head->first, first, new_first) != first);
Huang Ying781f7fd2011-09-08 14:00:45 +080047
Oleg Nesterovfb4214d2013-07-08 14:24:18 -070048 return !first;
Huang Yingf49f23a2011-07-13 13:14:23 +080049}
50EXPORT_SYMBOL_GPL(llist_add_batch);
51
52/**
53 * llist_del_first - delete the first entry of lock-less list
54 * @head: the head for your lock-less list
55 *
56 * If list is empty, return NULL, otherwise, return the first entry
57 * deleted, this is the newest added one.
58 *
59 * Only one llist_del_first user can be used simultaneously with
60 * multiple llist_add users without lock. Because otherwise
61 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
62 * llist_add) sequence in another user may change @head->first->next,
63 * but keep @head->first. If multiple consumers are needed, please
64 * use llist_del_all or use lock between consumers.
65 */
66struct llist_node *llist_del_first(struct llist_head *head)
67{
68 struct llist_node *entry, *old_entry, *next;
69
Huang Yingf49f23a2011-07-13 13:14:23 +080070 entry = head->first;
Huang Yinga3127332011-09-08 14:00:44 +080071 for (;;) {
Huang Yingf49f23a2011-07-13 13:14:23 +080072 if (entry == NULL)
73 return NULL;
74 old_entry = entry;
75 next = entry->next;
Huang Yinga3127332011-09-08 14:00:44 +080076 entry = cmpxchg(&head->first, old_entry, next);
77 if (entry == old_entry)
78 break;
Huang Yinga3127332011-09-08 14:00:44 +080079 }
Huang Yingf49f23a2011-07-13 13:14:23 +080080
81 return entry;
82}
83EXPORT_SYMBOL_GPL(llist_del_first);