llist.c

Go to the documentation of this file.

/*
 * 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 <[email protected]>
 *
 * 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 published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/llist.h>


bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
             struct llist_head *head)
{
    struct llist_node *entry, *old_entry;

    entry = head->first;
    for (;;) {
        old_entry = entry;
        new_last->next = entry;
        entry = cmpxchg(&head->first, old_entry, new_first);
        if (entry == old_entry)
            break;
    }

    return old_entry == NULL;
}
EXPORT_SYMBOL_GPL(llist_add_batch);

struct llist_node *llist_del_first(struct llist_head *head)
{
    struct llist_node *entry, *old_entry, *next;

    entry = head->first;
    for (;;) {
        if (entry == NULL)
            return NULL;
        old_entry = entry;
        next = entry->next;
        entry = cmpxchg(&head->first, old_entry, next);
        if (entry == old_entry)
            break;
    }

    return entry;
}
EXPORT_SYMBOL_GPL(llist_del_first);