Line data    Source code

       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/export.h>
      27             : #include <linux/interrupt.h>
      28             : #include <linux/llist.h>
      29             : 
      30             : 
      31             : /**
      32             :  * llist_add_batch - add several linked entries in batch
      33             :  * @new_first:  first entry in batch to be added
      34             :  * @new_last:   last entry in batch to be added
      35             :  * @head:       the head for your lock-less list
      36             :  *
      37             :  * Return whether list is empty before adding.
      38             :  */
      39        1790 : bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
      40             :                      struct llist_head *head)
      41             : {
      42             :         struct llist_node *first;
      43             : 
      44             :         do {
      45        1790 :                 new_last->next = first = ACCESS_ONCE(head->first);
      46        3580 :         } while (cmpxchg(&head->first, first, new_first) != first);
      47             : 
      48        1790 :         return !first;
      49             : }
      50             : EXPORT_SYMBOL_GPL(llist_add_batch);
      51             : 
      52             : /**
      53             :  * llist_del_first - delete the first entry of lock-less list
      54             :  * @head:       the head for your lock-less list
      55             :  *
      56             :  * If list is empty, return NULL, otherwise, return the first entry
      57             :  * deleted, this is the newest added one.
      58             :  *
      59             :  * Only one llist_del_first user can be used simultaneously with
      60             :  * multiple llist_add users without lock.  Because otherwise
      61             :  * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
      62             :  * llist_add) sequence in another user may change @head->first->next,
      63             :  * but keep @head->first.  If multiple consumers are needed, please
      64             :  * use llist_del_all or use lock between consumers.
      65             :  */
      66        1708 : struct llist_node *llist_del_first(struct llist_head *head)
      67             : {
      68             :         struct llist_node *entry, *old_entry, *next;
      69             : 
      70        1708 :         entry = head->first;
      71             :         for (;;) {
      72        1708 :                 if (entry == NULL)
      73             :                         return NULL;
      74             :                 old_entry = entry;
      75        1658 :                 next = entry->next;
      76        3316 :                 entry = cmpxchg(&head->first, old_entry, next);
      77        1658 :                 if (entry == old_entry)
      78             :                         break;
      79             :         }
      80             : 
      81             :         return entry;
      82             : }
      83             : EXPORT_SYMBOL_GPL(llist_del_first);
      84             : 
      85             : /**
      86             :  * llist_reverse_order - reverse order of a llist chain
      87             :  * @head:       first item of the list to be reversed
      88             :  *
      89             :  * Reverse the order of a chain of llist entries and return the
      90             :  * new first entry.
      91             :  */
      92           0 : struct llist_node *llist_reverse_order(struct llist_node *head)
      93             : {
      94             :         struct llist_node *new_head = NULL;
      95             : 
      96           0 :         while (head) {
      97             :                 struct llist_node *tmp = head;
      98           0 :                 head = head->next;
      99           0 :                 tmp->next = new_head;
     100             :                 new_head = tmp;
     101             :         }
     102             : 
     103           0 :         return new_head;
     104             : }
     105             : EXPORT_SYMBOL_GPL(llist_reverse_order);