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git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/blob - lib/llist.c
2 * Lock-less NULL terminated single linked list
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.
9 * Copyright 2010,2011 Intel Corp.
10 * Author: Huang Ying <ying.huang@intel.com>
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;
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.
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
25 #include <linux/kernel.h>
26 #include <linux/export.h>
27 #include <linux/llist.h>
31 * llist_add_batch - add several linked entries in batch
32 * @new_first: first entry in batch to be added
33 * @new_last: last entry in batch to be added
34 * @head: the head for your lock-less list
36 * Return whether list is empty before adding.
38 bool llist_add_batch(struct llist_node
*new_first
, struct llist_node
*new_last
,
39 struct llist_head
*head
)
41 struct llist_node
*first
;
44 new_last
->next
= first
= ACCESS_ONCE(head
->first
);
45 } while (cmpxchg(&head
->first
, first
, new_first
) != first
);
49 EXPORT_SYMBOL_GPL(llist_add_batch
);
52 * llist_del_first - delete the first entry of lock-less list
53 * @head: the head for your lock-less list
55 * If list is empty, return NULL, otherwise, return the first entry
56 * deleted, this is the newest added one.
58 * Only one llist_del_first user can be used simultaneously with
59 * multiple llist_add users without lock. Because otherwise
60 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
61 * llist_add) sequence in another user may change @head->first->next,
62 * but keep @head->first. If multiple consumers are needed, please
63 * use llist_del_all or use lock between consumers.
65 struct llist_node
*llist_del_first(struct llist_head
*head
)
67 struct llist_node
*entry
, *old_entry
, *next
;
69 entry
= smp_load_acquire(&head
->first
);
74 next
= READ_ONCE(entry
->next
);
75 entry
= cmpxchg(&head
->first
, old_entry
, next
);
76 if (entry
== old_entry
)
82 EXPORT_SYMBOL_GPL(llist_del_first
);
85 * llist_reverse_order - reverse order of a llist chain
86 * @head: first item of the list to be reversed
88 * Reverse the order of a chain of llist entries and return the
91 struct llist_node
*llist_reverse_order(struct llist_node
*head
)
93 struct llist_node
*new_head
= NULL
;
96 struct llist_node
*tmp
= head
;
104 EXPORT_SYMBOL_GPL(llist_reverse_order
);