needs_seqcst.rs

static A: AtomicU8 = AtomicU8::new(0);
static B: AtomicU8 = AtomicU8::new(0);
const ORDER: Ordering = ???;

let writer_0 = thread::spawn(|| {
    A.store(1, ORDER);
});

let writer_1 = thread::spawn(|| {
    B.store(1, ORDER);
});

let reader_0 = thread::spawn(|| -> bool {
    let a = A.load(ORDER);
    let b = B.load(ORDER);
    // `writer_0` went first
    a == 1 && b == 0
});
let reader_1 = thread::spawn(|| -> bool {
    let a = A.load(ORDER);
    let b = B.load(ORDER);
    // `writer_1` went first.
    a == 0 && b == 1
});
writer_0.join().unwrap();
writer_1.join().unwrap();
let writer_0_was_first = reader_0.join().unwrap();
let writer_1_was_first = reader_1.join().unwrap();
assert!(!(writer_0_was_first && writer_1_was_first));