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 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
 32/**
 33 * llist_add - add a new entry
 34 * @new:	new entry to be added
 35 * @head:	the head for your lock-less list
 36 */
 37void llist_add(struct llist_node *new, struct llist_head *head)
 38{
 39	struct llist_node *entry, *old_entry;
 40
 41#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 42	BUG_ON(in_nmi());
 43#endif
 44
 45	entry = head->first;
 46	do {
 47		old_entry = entry;
 48		new->next = entry;
 49		cpu_relax();
 50	} while ((entry = cmpxchg(&head->first, old_entry, new)) != old_entry);
 51}
 52EXPORT_SYMBOL_GPL(llist_add);
 53
 54/**
 55 * llist_add_batch - add several linked entries in batch
 56 * @new_first:	first entry in batch to be added
 57 * @new_last:	last entry in batch to be added
 58 * @head:	the head for your lock-less list
 
 
 59 */
 60void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
 61		     struct llist_head *head)
 62{
 63	struct llist_node *entry, *old_entry;
 64
 65#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 66	BUG_ON(in_nmi());
 67#endif
 68
 69	entry = head->first;
 70	do {
 71		old_entry = entry;
 72		new_last->next = entry;
 73		cpu_relax();
 74	} while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
 75}
 76EXPORT_SYMBOL_GPL(llist_add_batch);
 77
 78/**
 79 * llist_del_first - delete the first entry of lock-less list
 80 * @head:	the head for your lock-less list
 81 *
 82 * If list is empty, return NULL, otherwise, return the first entry
 83 * deleted, this is the newest added one.
 84 *
 85 * Only one llist_del_first user can be used simultaneously with
 86 * multiple llist_add users without lock.  Because otherwise
 87 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
 88 * llist_add) sequence in another user may change @head->first->next,
 89 * but keep @head->first.  If multiple consumers are needed, please
 90 * use llist_del_all or use lock between consumers.
 91 */
 92struct llist_node *llist_del_first(struct llist_head *head)
 93{
 94	struct llist_node *entry, *old_entry, *next;
 95
 96#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 97	BUG_ON(in_nmi());
 98#endif
 99
100	entry = head->first;
101	do {
102		if (entry == NULL)
103			return NULL;
104		old_entry = entry;
105		next = entry->next;
106		cpu_relax();
107	} while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);
 
 
108
109	return entry;
110}
111EXPORT_SYMBOL_GPL(llist_del_first);
112
113/**
114 * llist_del_all - delete all entries from lock-less list
115 * @head:	the head of lock-less list to delete all entries
116 *
117 * If list is empty, return NULL, otherwise, delete all entries and
118 * return the pointer to the first entry.  The order of entries
119 * deleted is from the newest to the oldest added one.
120 */
121struct llist_node *llist_del_all(struct llist_head *head)
122{
123#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
124	BUG_ON(in_nmi());
125#endif
 
 
 
 
 
126
127	return xchg(&head->first, NULL);
128}
129EXPORT_SYMBOL_GPL(llist_del_all);