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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Lock-less NULL terminated single linked list
4 *
5 * The basic atomic operation of this list is cmpxchg on long. On
6 * architectures that don't have NMI-safe cmpxchg implementation, the
7 * list can NOT be used in NMI handlers. So code that uses the list in
8 * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
9 *
10 * Copyright 2010,2011 Intel Corp.
11 * Author: Huang Ying <ying.huang@intel.com>
12 */
13#include <linux/kernel.h>
14#include <linux/export.h>
15#include <linux/llist.h>
16
17
18/**
19 * llist_add_batch - add several linked entries in batch
20 * @new_first: first entry in batch to be added
21 * @new_last: last entry in batch to be added
22 * @head: the head for your lock-less list
23 *
24 * Return whether list is empty before adding.
25 */
26bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
27 struct llist_head *head)
28{
29 struct llist_node *first;
30
31 do {
32 new_last->next = first = READ_ONCE(head->first);
33 } while (cmpxchg(&head->first, first, new_first) != first);
34
35 return !first;
36}
37EXPORT_SYMBOL_GPL(llist_add_batch);
38
39/**
40 * llist_del_first - delete the first entry of lock-less list
41 * @head: the head for your lock-less list
42 *
43 * If list is empty, return NULL, otherwise, return the first entry
44 * deleted, this is the newest added one.
45 *
46 * Only one llist_del_first user can be used simultaneously with
47 * multiple llist_add users without lock. Because otherwise
48 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
49 * llist_add) sequence in another user may change @head->first->next,
50 * but keep @head->first. If multiple consumers are needed, please
51 * use llist_del_all or use lock between consumers.
52 */
53struct llist_node *llist_del_first(struct llist_head *head)
54{
55 struct llist_node *entry, *old_entry, *next;
56
57 entry = smp_load_acquire(&head->first);
58 for (;;) {
59 if (entry == NULL)
60 return NULL;
61 old_entry = entry;
62 next = READ_ONCE(entry->next);
63 entry = cmpxchg(&head->first, old_entry, next);
64 if (entry == old_entry)
65 break;
66 }
67
68 return entry;
69}
70EXPORT_SYMBOL_GPL(llist_del_first);
71
72/**
73 * llist_reverse_order - reverse order of a llist chain
74 * @head: first item of the list to be reversed
75 *
76 * Reverse the order of a chain of llist entries and return the
77 * new first entry.
78 */
79struct llist_node *llist_reverse_order(struct llist_node *head)
80{
81 struct llist_node *new_head = NULL;
82
83 while (head) {
84 struct llist_node *tmp = head;
85 head = head->next;
86 tmp->next = new_head;
87 new_head = tmp;
88 }
89
90 return new_head;
91}
92EXPORT_SYMBOL_GPL(llist_reverse_order);
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 handlers. So code that uses the list in
7 * an NMI 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/export.h>
27#include <linux/interrupt.h>
28#include <linux/llist.h>
29
30
31/**
32 * 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
36 *
37 * Return whether list is empty before adding.
38 */
39bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
40 struct llist_head *head)
41{
42 struct llist_node *entry, *old_entry;
43
44 entry = head->first;
45 for (;;) {
46 old_entry = entry;
47 new_last->next = entry;
48 entry = cmpxchg(&head->first, old_entry, new_first);
49 if (entry == old_entry)
50 break;
51 }
52
53 return old_entry == NULL;
54}
55EXPORT_SYMBOL_GPL(llist_add_batch);
56
57/**
58 * llist_del_first - delete the first entry of lock-less list
59 * @head: the head for your lock-less list
60 *
61 * If list is empty, return NULL, otherwise, return the first entry
62 * deleted, this is the newest added one.
63 *
64 * Only one llist_del_first user can be used simultaneously with
65 * multiple llist_add users without lock. Because otherwise
66 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
67 * llist_add) sequence in another user may change @head->first->next,
68 * but keep @head->first. If multiple consumers are needed, please
69 * use llist_del_all or use lock between consumers.
70 */
71struct llist_node *llist_del_first(struct llist_head *head)
72{
73 struct llist_node *entry, *old_entry, *next;
74
75 entry = head->first;
76 for (;;) {
77 if (entry == NULL)
78 return NULL;
79 old_entry = entry;
80 next = entry->next;
81 entry = cmpxchg(&head->first, old_entry, next);
82 if (entry == old_entry)
83 break;
84 }
85
86 return entry;
87}
88EXPORT_SYMBOL_GPL(llist_del_first);