在golang中对uint8的读写是原子的吗？

Question

As in the title, are read and write operations regarding uint8, atomic? Logically it must be a single cpu instruction obviously to read and write for a 8 bit variable. But in any case, two cores could simultaneously read and write from the memory, is it possible to create a stale data this way?

Answer 1

There's no guarantee that the access on native types are on any platform atomic. This is why there is sync/atomic. See also the advice in the memory model documentation.

Example for generic way of atomically setting a value (Play)

var ax atomic.Value // may be globally accessible

x := uint8(5)

// set atomically
ax.Store(x)

x = ax.Load().(uint8)

Probably more efficient solution for uint8 (Play):

var ax int64 // may be globally accessible

x := uint8(5)

atomic.StoreInt64(&ax, 10)

x = uint8(atomic.LoadInt64(&ax))

fmt.Printf("%T %v
", x, x)