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  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
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has been chosen to replace the boilerplate/reference in 136 file(s).

Signed-off-by: Thomas Gleixner <>
Reviewed-by: Alexios Zavras <>
Reviewed-by: Allison Randal <>
Signed-off-by: Greg Kroah-Hartman <>
8 contributors

Users who have contributed to this file

@yhuang-intel @torvalds @paulgortmaker @utrace @Villemoes @dvyukov @dhowells @akpm00
// SPDX-License-Identifier: GPL-2.0-only
* Lock-less NULL terminated single linked list
* The basic atomic operation of this list is cmpxchg on long. On
* architectures that don't have NMI-safe cmpxchg implementation, the
* list can NOT be used in NMI handlers. So code that uses the list in
* an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
* Copyright 2010,2011 Intel Corp.
* Author: Huang Ying <>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/llist.h>
* llist_add_batch - add several linked entries in batch
* @new_first: first entry in batch to be added
* @new_last: last entry in batch to be added
* @head: the head for your lock-less list
* Return whether list is empty before adding.
bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
struct llist_head *head)
struct llist_node *first;
do {
new_last->next = first = READ_ONCE(head->first);
} while (cmpxchg(&head->first, first, new_first) != first);
return !first;
* llist_del_first - delete the first entry of lock-less list
* @head: the head for your lock-less list
* If list is empty, return NULL, otherwise, return the first entry
* deleted, this is the newest added one.
* Only one llist_del_first user can be used simultaneously with
* multiple llist_add users without lock. Because otherwise
* llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
* llist_add) sequence in another user may change @head->first->next,
* but keep @head->first. If multiple consumers are needed, please
* use llist_del_all or use lock between consumers.
struct llist_node *llist_del_first(struct llist_head *head)
struct llist_node *entry, *old_entry, *next;
entry = smp_load_acquire(&head->first);
for (;;) {
if (entry == NULL)
return NULL;
old_entry = entry;
next = READ_ONCE(entry->next);
entry = cmpxchg(&head->first, old_entry, next);
if (entry == old_entry)
return entry;
* llist_reverse_order - reverse order of a llist chain
* @head: first item of the list to be reversed
* Reverse the order of a chain of llist entries and return the
* new first entry.
struct llist_node *llist_reverse_order(struct llist_node *head)
struct llist_node *new_head = NULL;
while (head) {
struct llist_node *tmp = head;
head = head->next;
tmp->next = new_head;
new_head = tmp;
return new_head;