go - Mutex 似乎没有正确锁定

Question

我刚刚学习互斥。我以为下面的程序总共会返回 1000，但我得到的结果各不相同，所以我认为我做错了什么......

package main

import (
    "fmt"
    "sync"
)

var total int
var locker sync.RWMutex

func add() {
    for x := 1; x <= 100; x++ {
        locker.Lock()
        total += 1
        locker.Unlock()
    }
}

func main() {
    for x := 1; x <= 10; x++ {
        go add()
    }
    fmt.Printf("Total is %v\n", total)
}

Answer 1

Main 函数在 gorutines 完成它们的工作之前返回，你应该添加 sync.WaitGroup，这段代码如你所料:https://play.golang.com/p/_OfrZae0soB

package main

import (
    "fmt"
    "sync"
)

var total int
var locker sync.RWMutex

func add(wg *sync.WaitGroup) {
    defer wg.Done()
    for x := 1; x <= 100; x++ {
        locker.Lock()
        total += 1
        locker.Unlock()
    }
}

func main() {
    var wg sync.WaitGroup
    for x := 1; x <= 10; x++ {
        wg.Add(1)
        go add(&wg)
    }
    wg.Wait()
    fmt.Printf("Total is %v\n", total)
}