代码 let b = b_clone.load(Ordering::Relaxed); let a = a_clone.load(Ordering::Relaxed); 与 for i in 0..max_value { // fence(Ordering::SeqCst); a.store(i,Ordering::Relaxed); b.store(i, Ordering::Relaxed); } 它们之间是无序的，那么可能出 if b > a { println!("b is {}, a is {}", b, a); }的情况， 但是测试代码，从来没有出现过这种情况，无论运行多少次。请问有验证过可以的吗？

代码： https://gist.github.com/rust-play/0ca595b22ffba3f416cb88962ab5f51a

完整代码如下 ：

use std::sync::{Arc, Barrier}; use std::sync::atomic::{AtomicUsize, Ordering}; use std::thread;

fn main(){ let thread_num = num_cpus::get() -2; let max_value = 10000; let a = Arc::new(AtomicUsize::new(0)); let b = Arc::new(AtomicUsize::new(0)); let barrier = Arc::new(Barrier::new(thread_num + 1));

let mut threads = vec![];

for _ in 0..thread_num {
    let a_clone = a.clone();
    let b_clone = b.clone();
    let barrier_clone = barrier.clone();
    let t = thread::spawn(move ||{
        barrier_clone.wait();
        let mut v = 0;
        while v < max_value -1 {
            // fence(Ordering::SeqCst);
            let b = b_clone.load(Ordering::Relaxed);
            let a = a_clone.load(Ordering::Relaxed);

            if b > a {
                println!("b is {}, a is {}", b, a);
            }
            v = a;
        }
    });
    threads.push(t);
}

barrier.wait();
for i in 0..max_value {
    // fence(Ordering::SeqCst);
    a.store(i,Ordering::Relaxed);
    b.store(i, Ordering::Relaxed);
}

for t in threads {
    let _= t.join();
}

}