llist.h 6.24 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
#ifndef LLIST_H
#define LLIST_H
/*
 * Lock-less NULL terminated single linked list
 *
 * If there are multiple producers and multiple consumers, llist_add
 * can be used in producers and llist_del_all can be used in
 * consumers.  They can work simultaneously without lock.  But
 * llist_del_first can not be used here.  Because llist_del_first
 * depends on list->first->next does not changed if list->first is not
 * changed during its operation, but llist_del_first, llist_add,
 * llist_add (or llist_del_all, llist_add, llist_add) sequence in
 * another consumer may violate that.
 *
 * If there are multiple producers and one consumer, llist_add can be
 * used in producers and llist_del_all or llist_del_first can be used
 * in the consumer.
 *
 * This can be summarized as follow:
 *
 *           |   add    | del_first |  del_all
 * add       |    -     |     -     |     -
 * del_first |          |     L     |     L
 * del_all   |          |           |     -
 *
 * Where "-" stands for no lock is needed, while "L" stands for lock
 * is needed.
 *
 * The list entries deleted via llist_del_all can be traversed with
 * traversing function such as llist_for_each etc.  But the list
 * entries can not be traversed safely before deleted from the list.
 * The order of deleted entries is from the newest to the oldest added
 * one.  If you want to traverse from the oldest to the newest, you
 * must reverse the order by yourself before traversing.
 *
 * The basic atomic operation of this list is cmpxchg on long.  On
 * architectures that don't have NMI-safe cmpxchg implementation, the
38
39
 * list can NOT be used in NMI handlers.  So code that uses the list in
 * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
 *
 * Copyright 2010,2011 Intel Corp.
 *   Author: Huang Ying <ying.huang@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * 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
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
struct llist_head {
	struct llist_node *first;
};

struct llist_node {
	struct llist_node *next;
};

#define LLIST_HEAD_INIT(name)	{ NULL }
#define LLIST_HEAD(name)	struct llist_head name = LLIST_HEAD_INIT(name)

/**
 * init_llist_head - initialize lock-less list head
 * @head:	the head for your lock-less list
 */
static inline void init_llist_head(struct llist_head *list)
{
	list->first = NULL;
}

/**
 * llist_entry - get the struct of this entry
 * @ptr:	the &struct llist_node pointer.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the llist_node within the struct.
 */
#define llist_entry(ptr, type, member)		\
	container_of(ptr, type, member)

/**
 * llist_for_each - iterate over some deleted entries of a lock-less list
 * @pos:	the &struct llist_node to use as a loop cursor
 * @node:	the first entry of deleted list entries
 *
 * In general, some entries of the lock-less list can be traversed
 * safely only after being deleted from list, so start with an entry
 * instead of list head.
 *
 * If being used on entries deleted from lock-less list directly, the
 * traverse order is from the newest to the oldest added entry.  If
 * you want to traverse from the oldest to the newest, you must
 * reverse the order by yourself before traversing.
 */
#define llist_for_each(pos, node)			\
	for ((pos) = (node); pos; (pos) = (pos)->next)

/**
 * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
 * @pos:	the type * to use as a loop cursor.
 * @node:	the fist entry of deleted list entries.
 * @member:	the name of the llist_node with the struct.
 *
 * In general, some entries of the lock-less list can be traversed
 * safely only after being removed from list, so start with an entry
 * instead of list head.
 *
 * If being used on entries deleted from lock-less list directly, the
 * traverse order is from the newest to the oldest added entry.  If
 * you want to traverse from the oldest to the newest, you must
 * reverse the order by yourself before traversing.
 */
#define llist_for_each_entry(pos, node, member)				\
	for ((pos) = llist_entry((node), typeof(*(pos)), member);	\
	     &(pos)->member != NULL;					\
	     (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))

/**
 * llist_empty - tests whether a lock-less list is empty
 * @head:	the list to test
 *
 * Not guaranteed to be accurate or up to date.  Just a quick way to
 * test whether the list is empty without deleting something from the
 * list.
 */
135
static inline bool llist_empty(const struct llist_head *head)
136
137
138
139
{
	return ACCESS_ONCE(head->first) == NULL;
}

Peter Zijlstra's avatar
Peter Zijlstra committed
140
141
142
143
144
static inline struct llist_node *llist_next(struct llist_node *node)
{
	return node->next;
}

145
146
147
148
/**
 * llist_add - add a new entry
 * @new:	new entry to be added
 * @head:	the head for your lock-less list
149
 *
150
 * Returns true if the list was empty prior to adding this entry.
151
 */
152
static inline bool llist_add(struct llist_node *new, struct llist_head *head)
153
154
155
156
{
	struct llist_node *entry, *old_entry;

	entry = head->first;
157
	for (;;) {
158
159
		old_entry = entry;
		new->next = entry;
160
161
162
163
		entry = cmpxchg(&head->first, old_entry, new);
		if (entry == old_entry)
			break;
	}
164
165

	return old_entry == NULL;
166
167
168
169
170
171
172
173
174
175
176
177
178
179
}

/**
 * llist_del_all - delete all entries from lock-less list
 * @head:	the head of lock-less list to delete all entries
 *
 * If list is empty, return NULL, otherwise, delete all entries and
 * return the pointer to the first entry.  The order of entries
 * deleted is from the newest to the oldest added one.
 */
static inline struct llist_node *llist_del_all(struct llist_head *head)
{
	return xchg(&head->first, NULL);
}
180
181
182
183
184
185

extern bool llist_add_batch(struct llist_node *new_first,
			    struct llist_node *new_last,
			    struct llist_head *head);
extern struct llist_node *llist_del_first(struct llist_head *head);

186
#endif /* LLIST_H */