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1 : : #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
38 : : * 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.
40 : : *
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
56 : : */
57 : :
58 : : #include <linux/kernel.h>
59 : : #include <asm/cmpxchg.h>
60 : :
61 : : struct llist_head {
62 : : struct llist_node *first;
63 : : };
64 : :
65 : : struct 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 : : */
76 : : static inline void init_llist_head(struct llist_head *list)
77 : : {
78 : 248 : 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_for_each_entry_safe - iterate over some deleted entries of lock-less list of given type
129 : : * safe against removal of list entry
130 : : * @pos: the type * to use as a loop cursor.
131 : : * @n: another type * to use as temporary storage
132 : : * @node: the first entry of deleted list entries.
133 : : * @member: the name of the llist_node with the struct.
134 : : *
135 : : * In general, some entries of the lock-less list can be traversed
136 : : * safely only after being removed from list, so start with an entry
137 : : * instead of list head.
138 : : *
139 : : * If being used on entries deleted from lock-less list directly, the
140 : : * traverse order is from the newest to the oldest added entry. If
141 : : * you want to traverse from the oldest to the newest, you must
142 : : * reverse the order by yourself before traversing.
143 : : */
144 : : #define llist_for_each_entry_safe(pos, n, node, member) \
145 : : for (pos = llist_entry((node), typeof(*pos), member); \
146 : : &pos->member != NULL && \
147 : : (n = llist_entry(pos->member.next, typeof(*n), member), true); \
148 : : pos = n)
149 : :
150 : : /**
151 : : * llist_empty - tests whether a lock-less list is empty
152 : : * @head: the list to test
153 : : *
154 : : * Not guaranteed to be accurate or up to date. Just a quick way to
155 : : * test whether the list is empty without deleting something from the
156 : : * list.
157 : : */
158 : : static inline bool llist_empty(const struct llist_head *head)
159 : : {
160 : 25268994 : return ACCESS_ONCE(head->first) == NULL;
161 : : }
162 : :
163 : : static inline struct llist_node *llist_next(struct llist_node *node)
164 : : {
165 : 335352 : return node->next;
166 : : }
167 : :
168 : : extern bool llist_add_batch(struct llist_node *new_first,
169 : : struct llist_node *new_last,
170 : : struct llist_head *head);
171 : : /**
172 : : * llist_add - add a new entry
173 : : * @new: new entry to be added
174 : : * @head: the head for your lock-less list
175 : : *
176 : : * Returns true if the list was empty prior to adding this entry.
177 : : */
178 : : static inline bool llist_add(struct llist_node *new, struct llist_head *head)
179 : : {
180 : 384646 : return llist_add_batch(new, new, head);
181 : : }
182 : :
183 : : /**
184 : : * llist_del_all - delete all entries from lock-less list
185 : : * @head: the head of lock-less list to delete all entries
186 : : *
187 : : * If list is empty, return NULL, otherwise, delete all entries and
188 : : * return the pointer to the first entry. The order of entries
189 : : * deleted is from the newest to the oldest added one.
190 : : */
191 : : static inline struct llist_node *llist_del_all(struct llist_head *head)
192 : : {
193 : 673614 : return xchg(&head->first, NULL);
194 : : }
195 : :
196 : : extern struct llist_node *llist_del_first(struct llist_head *head);
197 : :
198 : : struct llist_node *llist_reverse_order(struct llist_node *head);
199 : :
200 : : #endif /* LLIST_H */
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