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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 handlers. So code that uses the list in |
7 | * an NMI 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_batch - add several linked entries in batch |
34 | * @new_first: first entry in batch to be added |
35 | * @new_last: last entry in batch to be added |
36 | * @head: the head for your lock-less list |
37 | * |
38 | * Return whether list is empty before adding. |
39 | */ |
40 | bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last, |
41 | struct llist_head *head) |
42 | { |
43 | struct llist_node *entry, *old_entry; |
44 | |
45 | entry = head->first; |
46 | for (;;) { |
47 | old_entry = entry; |
48 | new_last->next = entry; |
49 | entry = cmpxchg(&head->first, old_entry, new_first); |
50 | if (entry == old_entry) |
51 | break; |
52 | } |
53 | |
54 | return old_entry == NULL; |
55 | } |
56 | EXPORT_SYMBOL_GPL(llist_add_batch); |
57 | |
58 | /** |
59 | * llist_del_first - delete the first entry of lock-less list |
60 | * @head: the head for your lock-less list |
61 | * |
62 | * If list is empty, return NULL, otherwise, return the first entry |
63 | * deleted, this is the newest added one. |
64 | * |
65 | * Only one llist_del_first user can be used simultaneously with |
66 | * multiple llist_add users without lock. Because otherwise |
67 | * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add, |
68 | * llist_add) sequence in another user may change @head->first->next, |
69 | * but keep @head->first. If multiple consumers are needed, please |
70 | * use llist_del_all or use lock between consumers. |
71 | */ |
72 | struct llist_node *llist_del_first(struct llist_head *head) |
73 | { |
74 | struct llist_node *entry, *old_entry, *next; |
75 | |
76 | entry = head->first; |
77 | for (;;) { |
78 | if (entry == NULL) |
79 | return NULL; |
80 | old_entry = entry; |
81 | next = entry->next; |
82 | entry = cmpxchg(&head->first, old_entry, next); |
83 | if (entry == old_entry) |
84 | break; |
85 | } |
86 | |
87 | return entry; |
88 | } |
89 | EXPORT_SYMBOL_GPL(llist_del_first); |
90 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9