Branch data Line data Source code
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/export.h>
27 : : #include <linux/interrupt.h>
28 : : #include <linux/llist.h>
29 : :
30 : :
31 : : /**
32 : : * llist_add_batch - add several linked entries in batch
33 : : * @new_first: first entry in batch to be added
34 : : * @new_last: last entry in batch to be added
35 : : * @head: the head for your lock-less list
36 : : *
37 : : * Return whether list is empty before adding.
38 : : */
39 : 385080 : bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
40 : : struct llist_head *head)
41 : : {
42 : : struct llist_node *first;
43 : :
44 : : do {
45 : 385080 : new_last->next = first = ACCESS_ONCE(head->first);
46 [ - + ]: 770160 : } while (cmpxchg(&head->first, first, new_first) != first);
47 : :
48 : 385080 : return !first;
49 : : }
50 : : EXPORT_SYMBOL_GPL(llist_add_batch);
51 : :
52 : : /**
53 : : * llist_del_first - delete the first entry of lock-less list
54 : : * @head: the head for your lock-less list
55 : : *
56 : : * If list is empty, return NULL, otherwise, return the first entry
57 : : * deleted, this is the newest added one.
58 : : *
59 : : * Only one llist_del_first user can be used simultaneously with
60 : : * multiple llist_add users without lock. Because otherwise
61 : : * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
62 : : * llist_add) sequence in another user may change @head->first->next,
63 : : * but keep @head->first. If multiple consumers are needed, please
64 : : * use llist_del_all or use lock between consumers.
65 : : */
66 : 0 : struct llist_node *llist_del_first(struct llist_head *head)
67 : : {
68 : : struct llist_node *entry, *old_entry, *next;
69 : :
70 : 49294 : entry = head->first;
71 : : for (;;) {
72 [ + + ]: 49295 : if (entry == NULL)
73 : : return NULL;
74 : : old_entry = entry;
75 : 49255 : next = entry->next;
76 : 98510 : entry = cmpxchg(&head->first, old_entry, next);
77 [ + + ]: 49255 : if (entry == old_entry)
78 : : break;
79 : : }
80 : :
81 : : return entry;
82 : : }
83 : : EXPORT_SYMBOL_GPL(llist_del_first);
84 : :
85 : : /**
86 : : * llist_reverse_order - reverse order of a llist chain
87 : : * @head: first item of the list to be reversed
88 : : *
89 : : * Reverse the order of a chain of llist entries and return the
90 : : * new first entry.
91 : : */
92 : 0 : struct llist_node *llist_reverse_order(struct llist_node *head)
93 : : {
94 : : struct llist_node *new_head = NULL;
95 : :
96 [ # # ]: 0 : while (head) {
97 : : struct llist_node *tmp = head;
98 : 0 : head = head->next;
99 : 0 : tmp->next = new_head;
100 : : new_head = tmp;
101 : : }
102 : :
103 : 0 : return new_head;
104 : : }
105 : : EXPORT_SYMBOL_GPL(llist_reverse_order);
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