Function deadlock

mysys/waiting_threads.c:856–906

Deadlock detection in a wait-for graph A wrapper for recursive deadlock_search() - prepares deadlock_arg structure, invokes deadlock_search(), increments statistics, notifies the victim. @param thd thread that is going to wait. Deadlock is detected if, while walking the graph, we reach a thread that is waiting on thd @param block

  @param max_depth      search depth limit
*/
static int deadlock(WT_THD *thd, WT_THD *blocker, uint depth,
                            uint max_depth)
{
  struct deadlock_arg arg= {thd, max_depth, 0, 0};
  int ret;
  DBUG_ENTER("deadlock");
  DBUG_ASSERT(depth < 2);
  ret= deadlock_search(&arg, blocker, depth);
  if (ret == WT_DEPTH_EXCEEDED)
  {
    increment_cycle_stats(WT_CYCLE_STATS, max_depth ==
                                          *thd->deadlock_search_depth_long);
    ret= WT_OK;
  }
  /*
    if we started with depth==1, blocker was never considered for a victim
    in deadlock_search(). Do it here.
  */
  if (ret == WT_DEADLOCK && depth)
    change_victim(blocker, &arg);
  if (arg.last_locked_rc)
  {
    /*
      Special return code if there's nobody to wait for.

      depth == 0 means that we start the search from thd (thd == blocker).
      ret == WT_OK means that no cycle was found and
        arg.last_locked_rc == thd->waiting_for.
      and arg.last_locked_rc->owners.elements == 0 means that
        (applying the rule above) thd->waiting_for->owners.elements == 0,
        and thd doesn't have anybody to wait for.
    */
    if (depth == 0 && ret == WT_OK && arg.last_locked_rc->owners.elements == 0)
    {
      DBUG_ASSERT(thd == blocker);
      DBUG_ASSERT(arg.last_locked_rc == thd->waiting_for);
      ret= WT_FREE_TO_GO;
    }
    rc_unlock(arg.last_locked_rc);
  }
  /* notify the victim, if appropriate */
  if (ret == WT_DEADLOCK && arg.victim != thd)
  {
    DBUG_PRINT("wt", ("killing %s", arg.victim->name));
    arg.victim->killed= 1;
    mysql_cond_broadcast(&arg.victim->waiting_for->cond);
    rc_unlock(arg.victim->waiting_for);
    ret= WT_OK;
  }
  DBUG_RETURN(ret);
}


/**