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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 | */ |
37 | void 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 | } |
52 | EXPORT_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 | */ |
60 | void 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 | } |
76 | EXPORT_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 | */ |
92 | struct 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 | } |
111 | EXPORT_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 | */ |
121 | struct 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 | } |
129 | EXPORT_SYMBOL_GPL(llist_del_all); |
130 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
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