> Even through the compiler will read a `volatile` variable from memory every time, that memory may still have a stale value in the CPU cache, which `volatile` will do nothing to prevent

FWIW, it doesn't even do this, it's just a compiler-level annotation:

  volatile int x = 0;
  int foo() {
    // read
    int ret = x;
    (void)x;

    // write
    x = 0;
    x = 1;

    return ret;
  }

The 'volatile' ensures that that code results in two reads and two writes. Removing it allows the compiler to optimise down to the equivalent of 'int ret = x; x = 1; return ret;', but both with and without use the exact same read/write instructions (i.e. have the same interaction with the cache): mov on x86 and ldr/str on ARM.