1 #ifndef __TOOLS_LINUX_LLIST_H
2 #define __TOOLS_LINUX_LLIST_H
5 * Lock-less NULL terminated single linked list
7 * If there are multiple producers and multiple consumers, llist_add
8 * can be used in producers and llist_del_all can be used in
9 * consumers. They can work simultaneously without lock. But
10 * llist_del_first can not be used here. Because llist_del_first
11 * depends on list->first->next does not changed if list->first is not
12 * changed during its operation, but llist_del_first, llist_add,
13 * llist_add (or llist_del_all, llist_add, llist_add) sequence in
14 * another consumer may violate that.
16 * If there are multiple producers and one consumer, llist_add can be
17 * used in producers and llist_del_all or llist_del_first can be used
20 * This can be summarized as follow:
22 * | add | del_first | del_all
27 * Where "-" stands for no lock is needed, while "L" stands for lock
30 * The list entries deleted via llist_del_all can be traversed with
31 * traversing function such as llist_for_each etc. But the list
32 * entries can not be traversed safely before deleted from the list.
33 * The order of deleted entries is from the newest to the oldest added
34 * one. If you want to traverse from the oldest to the newest, you
35 * must reverse the order by yourself before traversing.
37 * The basic atomic operation of this list is cmpxchg on long. On
38 * architectures that don't have NMI-safe cmpxchg implementation, the
39 * list can NOT be used in NMI handlers. So code that uses the list in
40 * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
42 * Copyright 2010,2011 Intel Corp.
43 * Author: Huang Ying <ying.huang@intel.com>
45 * This program is free software; you can redistribute it and/or
46 * modify it under the terms of the GNU General Public License version
47 * 2 as published by the Free Software Foundation;
49 * This program is distributed in the hope that it will be useful,
50 * but WITHOUT ANY WARRANTY; without even the implied warranty of
51 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
52 * GNU General Public License for more details.
54 * You should have received a copy of the GNU General Public License
55 * along with this program; if not, write to the Free Software
56 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
59 #include <linux/atomic.h>
60 #include <linux/kernel.h>
63 struct llist_node *first;
67 struct llist_node *next;
70 #define LLIST_HEAD_INIT(name) { NULL }
71 #define LLIST_HEAD(name) struct llist_head name = LLIST_HEAD_INIT(name)
74 * init_llist_head - initialize lock-less list head
75 * @head: the head for your lock-less list
77 static inline void init_llist_head(struct llist_head *list)
83 * llist_entry - get the struct of this entry
84 * @ptr: the &struct llist_node pointer.
85 * @type: the type of the struct this is embedded in.
86 * @member: the name of the llist_node within the struct.
88 #define llist_entry(ptr, type, member) \
89 container_of(ptr, type, member)
92 * llist_for_each - iterate over some deleted entries of a lock-less list
93 * @pos: the &struct llist_node to use as a loop cursor
94 * @node: the first entry of deleted list entries
96 * In general, some entries of the lock-less list can be traversed
97 * safely only after being deleted from list, so start with an entry
98 * instead of list head.
100 * If being used on entries deleted from lock-less list directly, the
101 * traverse order is from the newest to the oldest added entry. If
102 * you want to traverse from the oldest to the newest, you must
103 * reverse the order by yourself before traversing.
105 #define llist_for_each(pos, node) \
106 for ((pos) = (node); pos; (pos) = (pos)->next)
109 * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
110 * @pos: the type * to use as a loop cursor.
111 * @node: the fist entry of deleted list entries.
112 * @member: the name of the llist_node with the struct.
114 * In general, some entries of the lock-less list can be traversed
115 * safely only after being removed from list, so start with an entry
116 * instead of list head.
118 * If being used on entries deleted from lock-less list directly, the
119 * traverse order is from the newest to the oldest added entry. If
120 * you want to traverse from the oldest to the newest, you must
121 * reverse the order by yourself before traversing.
123 #define llist_for_each_entry(pos, node, member) \
124 for ((pos) = llist_entry((node), typeof(*(pos)), member); \
125 &(pos)->member != NULL; \
126 (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))
129 * llist_for_each_entry_safe - iterate over some deleted entries of lock-less list of given type
130 * safe against removal of list entry
131 * @pos: the type * to use as a loop cursor.
132 * @n: another type * to use as temporary storage
133 * @node: the first entry of deleted list entries.
134 * @member: the name of the llist_node with the struct.
136 * In general, some entries of the lock-less list can be traversed
137 * safely only after being removed from list, so start with an entry
138 * instead of list head.
140 * If being used on entries deleted from lock-less list directly, the
141 * traverse order is from the newest to the oldest added entry. If
142 * you want to traverse from the oldest to the newest, you must
143 * reverse the order by yourself before traversing.
145 #define llist_for_each_entry_safe(pos, n, node, member) \
146 for (pos = llist_entry((node), typeof(*pos), member); \
147 &pos->member != NULL && \
148 (n = llist_entry(pos->member.next, typeof(*n), member), true); \
152 * llist_empty - tests whether a lock-less list is empty
153 * @head: the list to test
155 * Not guaranteed to be accurate or up to date. Just a quick way to
156 * test whether the list is empty without deleting something from the
159 static inline bool llist_empty(const struct llist_head *head)
161 return ACCESS_ONCE(head->first) == NULL;
164 static inline struct llist_node *llist_next(struct llist_node *node)
169 extern bool llist_add_batch(struct llist_node *new_first,
170 struct llist_node *new_last,
171 struct llist_head *head);
173 * llist_add - add a new entry
174 * @new: new entry to be added
175 * @head: the head for your lock-less list
177 * Returns true if the list was empty prior to adding this entry.
179 static inline bool llist_add(struct llist_node *new, struct llist_head *head)
181 return llist_add_batch(new, new, head);
185 * llist_del_all - delete all entries from lock-less list
186 * @head: the head of lock-less list to delete all entries
188 * If list is empty, return NULL, otherwise, delete all entries and
189 * return the pointer to the first entry. The order of entries
190 * deleted is from the newest to the oldest added one.
192 static inline struct llist_node *llist_del_all(struct llist_head *head)
194 return xchg(&head->first, NULL);
197 extern struct llist_node *llist_del_first(struct llist_head *head);
199 struct llist_node *llist_reverse_order(struct llist_node *head);
201 #endif /* __TOOLS_LINUX_LLIST_H */