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Huang Yingf49f23a2011-07-13 13:14:23 +08001#ifndef LLIST_H
2#define LLIST_H
3/*
4 * Lock-less NULL terminated single linked list
5 *
6 * If there are multiple producers and multiple consumers, llist_add
7 * can be used in producers and llist_del_all can be used in
8 * consumers. They can work simultaneously without lock. But
9 * llist_del_first can not be used here. Because llist_del_first
10 * depends on list->first->next does not changed if list->first is not
11 * changed during its operation, but llist_del_first, llist_add,
12 * llist_add (or llist_del_all, llist_add, llist_add) sequence in
13 * another consumer may violate that.
14 *
15 * If there are multiple producers and one consumer, llist_add can be
16 * used in producers and llist_del_all or llist_del_first can be used
17 * in the consumer.
18 *
19 * This can be summarized as follow:
20 *
21 * | add | del_first | del_all
22 * add | - | - | -
23 * del_first | | L | L
24 * del_all | | | -
25 *
26 * Where "-" stands for no lock is needed, while "L" stands for lock
27 * is needed.
28 *
29 * The list entries deleted via llist_del_all can be traversed with
30 * traversing function such as llist_for_each etc. But the list
31 * entries can not be traversed safely before deleted from the list.
32 * The order of deleted entries is from the newest to the oldest added
33 * one. If you want to traverse from the oldest to the newest, you
34 * must reverse the order by yourself before traversing.
35 *
36 * The basic atomic operation of this list is cmpxchg on long. On
37 * architectures that don't have NMI-safe cmpxchg implementation, the
Ingo Molnar2c302452011-10-04 12:43:11 +020038 * list can NOT be used in NMI handlers. So code that uses the list in
39 * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
Huang Ying1230db82011-09-08 14:00:42 +080040 *
41 * Copyright 2010,2011 Intel Corp.
42 * Author: Huang Ying <ying.huang@intel.com>
43 *
44 * This program is free software; you can redistribute it and/or
45 * modify it under the terms of the GNU General Public License version
46 * 2 as published by the Free Software Foundation;
47 *
48 * This program is distributed in the hope that it will be useful,
49 * but WITHOUT ANY WARRANTY; without even the implied warranty of
50 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
51 * GNU General Public License for more details.
52 *
53 * You should have received a copy of the GNU General Public License
54 * along with this program; if not, write to the Free Software
55 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Huang Yingf49f23a2011-07-13 13:14:23 +080056 */
57
Huang Ying1230db82011-09-08 14:00:42 +080058#include <linux/kernel.h>
David Howells96f951e2012-03-28 18:30:03 +010059#include <asm/cmpxchg.h>
Huang Ying1230db82011-09-08 14:00:42 +080060
Huang Yingf49f23a2011-07-13 13:14:23 +080061struct llist_head {
62 struct llist_node *first;
63};
64
65struct llist_node {
66 struct llist_node *next;
67};
68
69#define LLIST_HEAD_INIT(name) { NULL }
70#define LLIST_HEAD(name) struct llist_head name = LLIST_HEAD_INIT(name)
71
72/**
73 * init_llist_head - initialize lock-less list head
74 * @head: the head for your lock-less list
75 */
76static inline void init_llist_head(struct llist_head *list)
77{
78 list->first = NULL;
79}
80
81/**
82 * llist_entry - get the struct of this entry
83 * @ptr: the &struct llist_node pointer.
84 * @type: the type of the struct this is embedded in.
85 * @member: the name of the llist_node within the struct.
86 */
87#define llist_entry(ptr, type, member) \
88 container_of(ptr, type, member)
89
90/**
91 * llist_for_each - iterate over some deleted entries of a lock-less list
92 * @pos: the &struct llist_node to use as a loop cursor
93 * @node: the first entry of deleted list entries
94 *
95 * In general, some entries of the lock-less list can be traversed
96 * safely only after being deleted from list, so start with an entry
97 * instead of list head.
98 *
99 * If being used on entries deleted from lock-less list directly, the
100 * traverse order is from the newest to the oldest added entry. If
101 * you want to traverse from the oldest to the newest, you must
102 * reverse the order by yourself before traversing.
103 */
104#define llist_for_each(pos, node) \
105 for ((pos) = (node); pos; (pos) = (pos)->next)
106
107/**
108 * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
109 * @pos: the type * to use as a loop cursor.
110 * @node: the fist entry of deleted list entries.
111 * @member: the name of the llist_node with the struct.
112 *
113 * In general, some entries of the lock-less list can be traversed
114 * safely only after being removed from list, so start with an entry
115 * instead of list head.
116 *
117 * If being used on entries deleted from lock-less list directly, the
118 * traverse order is from the newest to the oldest added entry. If
119 * you want to traverse from the oldest to the newest, you must
120 * reverse the order by yourself before traversing.
121 */
122#define llist_for_each_entry(pos, node, member) \
123 for ((pos) = llist_entry((node), typeof(*(pos)), member); \
124 &(pos)->member != NULL; \
125 (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))
126
127/**
128 * llist_empty - tests whether a lock-less list is empty
129 * @head: the list to test
130 *
131 * Not guaranteed to be accurate or up to date. Just a quick way to
132 * test whether the list is empty without deleting something from the
133 * list.
134 */
Huang Ying1230db82011-09-08 14:00:42 +0800135static inline bool llist_empty(const struct llist_head *head)
Huang Yingf49f23a2011-07-13 13:14:23 +0800136{
137 return ACCESS_ONCE(head->first) == NULL;
138}
139
Peter Zijlstra924f8f52011-09-12 13:12:28 +0200140static inline struct llist_node *llist_next(struct llist_node *node)
141{
142 return node->next;
143}
144
Huang Ying1230db82011-09-08 14:00:42 +0800145/**
146 * llist_add - add a new entry
147 * @new: new entry to be added
148 * @head: the head for your lock-less list
Huang Ying781f7fd2011-09-08 14:00:45 +0800149 *
Andrew Mortonfc23af32011-10-31 17:13:08 -0700150 * Returns true if the list was empty prior to adding this entry.
Huang Ying1230db82011-09-08 14:00:42 +0800151 */
Huang Ying781f7fd2011-09-08 14:00:45 +0800152static inline bool llist_add(struct llist_node *new, struct llist_head *head)
Huang Ying1230db82011-09-08 14:00:42 +0800153{
154 struct llist_node *entry, *old_entry;
155
Huang Ying1230db82011-09-08 14:00:42 +0800156 entry = head->first;
Huang Yinga3127332011-09-08 14:00:44 +0800157 for (;;) {
Huang Ying1230db82011-09-08 14:00:42 +0800158 old_entry = entry;
159 new->next = entry;
Huang Yinga3127332011-09-08 14:00:44 +0800160 entry = cmpxchg(&head->first, old_entry, new);
161 if (entry == old_entry)
162 break;
Huang Yinga3127332011-09-08 14:00:44 +0800163 }
Huang Ying781f7fd2011-09-08 14:00:45 +0800164
165 return old_entry == NULL;
Huang Ying1230db82011-09-08 14:00:42 +0800166}
167
168/**
169 * llist_del_all - delete all entries from lock-less list
170 * @head: the head of lock-less list to delete all entries
171 *
172 * If list is empty, return NULL, otherwise, delete all entries and
173 * return the pointer to the first entry. The order of entries
174 * deleted is from the newest to the oldest added one.
175 */
176static inline struct llist_node *llist_del_all(struct llist_head *head)
177{
Huang Ying1230db82011-09-08 14:00:42 +0800178 return xchg(&head->first, NULL);
179}
Stephen Rothwell540f41e2011-10-05 17:25:28 +1100180
181extern bool llist_add_batch(struct llist_node *new_first,
182 struct llist_node *new_last,
183 struct llist_head *head);
184extern struct llist_node *llist_del_first(struct llist_head *head);
185
Huang Yingf49f23a2011-07-13 13:14:23 +0800186#endif /* LLIST_H */