Unsafe: storeFence() & loadFence() vs volatile

Question

I'm checking this great post on java fences, in which fences are used for following example, to ensure that concurrent thread can always read latest value updated from other threads:

// CPU 0:
void shutDownWithFailure(void)
{
  failure = 1; // must use SOB as this is owned by CPU 1
  SFENCE // next instruction will execute after all SOBs are processed
  shutdown = 1; // can execute immediately as it is owned be CPU 0
}
// CPU1:
void workLoop(void)
{
  while (shutdown == 0) { ... }
  LFENCE // next instruction will execute after all LOBs are processed
  if (failure) { ...}
}

My question is, what's the advantage of using fences against volatile.
Taking above example, if I make both failure and shutdown volatile, it should achieve the same?

Answer 1

I would say, it's all described in the JEP 171 that is linked to that question, in the "Motivation" section at the top. To sum it up: it is meant to provide a documented way to access these mechanisms and to provide further implementations and extensions of the classes for concurrent access.

Doesn't mean to use them is always an advantage over volatile.