Method lock

kernel/oswrapper/vspace.h:385–393

    vmem_free(_lock);
  }
  void lock() {
    if (_owner == vmem.current_process) {
      _locklevel++;
    } else {
      lock_file(vmem.fd, METABLOCK_SIZE + _lock);
      _owner = vmem.current_process;
      _locklevel = 1;
    }
  }
  void unlock() {
    if (--_locklevel == 0) {
      assert(_owner == vmem.current_process);