go - 如何两次解锁互斥锁

Question

两次解锁互斥体是否安全？我的代码:

var m sync.RWMutex = sync.RWMutex{}

func Read() {
    m.RLock()
    defer m.RUnlock()

    // Do something that needs lock
    err := SomeFunction1()
    if err != nil {
        return
    }

    m.RUnlock()

    // Do something that does not need lock
    SomeFunction2()

}

我需要defer m.RUnlock()来应对SomeFunction1()返回错误的情况。但是当 SomeFunction1() 返回且没有错误时，m 将被 m.RUnlock() 和 defer m.RUnlock( 解锁两次)。

两次解锁互斥体是否安全？如果没有，我应该如何修复我的代码？

Answer 1

Is it safe for unlocking a mutex twice?

不，您不应该两次解锁互斥体。根据docs，这是一个运行时错误 .

RUnlock undoes a single RLock call; it does not affect other simultaneous readers. It is a run-time error if rw is not locked for reading on entry to RUnlock.

<小时/>

If not, how should I fix my code?

我建议保留defer，但仅保留m.RUnlock()以防出现错误。如果您在 SomeFunction1() 和 SomeFunction2() 之间添加更多函数调用，这可以轻松扩展。

func Read() {
    var err error
    m.RLock()
    defer func() {
        if err != nil {
            m.RUnlock()
        }
    }()
    

    // Do something that needs lock
    err = SomeFunction1()
    if err != nil {
        return
    }

    m.RUnlock()

    // Do something that does not need lock
    SomeFunction2()
}

试试 Go Playground !