Root/lib/llist.c

Source at commit b386be689295730688885552666ea40b2e639b14 created 8 years 11 months ago.
By Maarten ter Huurne, Revert "MIPS: JZ4740: reset: Initialize hibernate wakeup counters."
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 */
40bool 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}
56EXPORT_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 */
72struct 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}
89EXPORT_SYMBOL_GPL(llist_del_first);
90

Archive Download this file



interactive