SonarCloud found this today after JDK-8352251 integration. In JfrSamplerThread::task_stacktrace, there seems to be a commented-out limited stack walk:

void JfrSamplerThread::task_stacktrace(JfrSampleRequestType type, JavaThread** last_thread) {
  const uint sample_limit = JAVA_SAMPLE == type ? 5 : 1; /// <--- UNUSED
  ...
    // while (num_samples < sample_limit) { /// <--- HERE
    while (true) {

Is this a debugging left-over? Or is it something we actually want?