BLI_linklist_lockfree.c

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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
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2018 Blender Foundation.
 * All rights reserved.
 */
 
#include "MEM_guardedalloc.h"
 
#include "BLI_linklist_lockfree.h"
#include "BLI_strict_flags.h"
 
#include "atomic_ops.h"
 
void BLI_linklist_lockfree_init(LockfreeLinkList *list)
{
  list->dummy_node.next = NULL;
  list->head = list->tail = &list->dummy_node;
}
 
void BLI_linklist_lockfree_free(LockfreeLinkList *list, LockfreeeLinkNodeFreeFP free_func)
{
  if (free_func != NULL) {
    /* NOTE: We start from a first user-added node. */
    LockfreeLinkNode *node = list->head->next;
    while (node != NULL) {
      LockfreeLinkNode *node_next = node->next;
      free_func(node);
      node = node_next;
    }
  }
}
 
void BLI_linklist_lockfree_clear(LockfreeLinkList *list, LockfreeeLinkNodeFreeFP free_func)
{
  BLI_linklist_lockfree_free(list, free_func);
  BLI_linklist_lockfree_init(list);
}
 
void BLI_linklist_lockfree_insert(LockfreeLinkList *list, LockfreeLinkNode *node)
{
  /* Based on:
   *
   * John D. Valois
   * Implementing Lock-Free Queues
   *
   * http://people.csail.mit.edu/bushl2/rpi/portfolio/lockfree-grape/documents/lock-free-linked-lists.pdf
   */
  bool keep_working;
  LockfreeLinkNode *tail_node;
  node->next = NULL;
  do {
    tail_node = list->tail;
    keep_working = (atomic_cas_ptr((void **)&tail_node->next, NULL, node) != NULL);
    if (keep_working) {
      atomic_cas_ptr((void **)&list->tail, tail_node, tail_node->next);
    }
  } while (keep_working);
  atomic_cas_ptr((void **)&list->tail, tail_node, node);
}
 
LockfreeLinkNode *BLI_linklist_lockfree_begin(LockfreeLinkList *list)
{
  return list->head->next;
}