void RenderThreadImpl::PreCacheFontCharacters(const LOGFONT& log_font,
                                              const base::string16& str) {
  Send(new ViewHostMsg_PreCacheFontCharacters(log_font, str));
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.