/*
   * 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 <ying.huang@intel.com>
   *
   * 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>
  
  
  /**
   * 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 = ACCESS_ONCE(head->first);
  	} while (cmpxchg(&head->first, first, new_first) != first);
  
  	return !first;
  }
  EXPORT_SYMBOL_GPL(llist_add_batch);
  
  /**
   * 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 = 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);
  
  /**
   * 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;
  }
  EXPORT_SYMBOL_GPL(llist_reverse_order);