内存 – golang中的原子操作是否建立了先发生关系？

发布时间：2020-12-16 09:25:52 所属栏目：大数据来源：网络整理

导读：我知道可以发生g打印2然后给出以下代码0. var a,b uint32func f() { a = 1 b = 2}func g() { fmt.Println(b) fmt.Println(a)}func main() { go f() g()} 如果我将所有读写更改为原子操作怎么办？是否保证如果g先打印2,那么还会打印1？ var a,b uint32func f(

我知道可以发生g打印2然后给出以下代码0.

var a,b uint32

func f() {
    a = 1
    b = 2
}

func g() {
    fmt.Println(b)
    fmt.Println(a)
}

func main() {
    go f()
    g()
}

如果我将所有读写更改为原子操作怎么办？是否保证如果g先打印2,那么还会打印1？

var a,b uint32

func f() {
    atomic.StoreUint32(&a,1)
    atomic.StoreUint32(&b,2)
}

func g() {
    fmt.Println(atomic.LoadUint32(&b))
    fmt.Println(atomic.LoadUint32(&a))
}

func main() {
    go f()
    g()
}

解决方法

没有.没有同步,所以没有 “happens before”的关系.

goroutines之间的Synchronization是通过通道通信和锁定操作完成的.

内存模型中的关键段落是：

Within a single goroutine,reads and writes must behave as if they executed in the order specified by the program. That is,compilers and processors may reorder the reads and writes executed within a single goroutine only when the reordering does not change the behavior within that goroutine as defined by the language specification. Because of this reordering,the execution order observed by one goroutine may differ from the order perceived by another. For example,if one goroutine executes a = 1; b = 2;,another might observe the updated value of b before the updated value of a.

（编辑：李大同）

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