GO 锁

不加锁

package main

import (
    "fmt"
    "sync"
)

var x=0
var wg107 sync.WaitGroup

func add1() {
    for i := 0; i < 50000; i++ {
        x += 1
    }
    wg107.Done()
}


func test1() {
    wg107.Add(2)
    go add1()
    go add1()
    wg107.Wait()
    fmt.Println("Done ~", x)
}


func main() {
    test1()
}

执行1：Done ~ 59534

执行2：Done ~ 50243

可以看出每次执行结果不一，原因：共有变量x，没加锁，导致可能同时获取到加1，导致只加了1次

互斥锁

package main

import (
    "fmt"
    "sync"
)

var x=0
var wg107 sync.WaitGroup
var lock sync.Mutex


func add2() {
    for i := 0; i < 50000; i++ {
        lock.Lock()
        x += 1
        lock.Unlock()
    }
    wg107.Done()
}

func test2() {
    wg107.Add(2)
    go add2()
    go add2()
    wg107.Wait()
    fmt.Println("Done ~", x)
}

func main() {
    test2()
}

读写互斥锁

package main

import (
    "fmt"
    "sync"
    "time"
)

var x = 0
var wg107 sync.WaitGroup

var rwlock sync.RWMutex

func read() {
    defer wg107.Done()
    rwlock.RLock()
    time.Sleep(time.Millisecond)
    rwlock.RUnlock()
}

func write() {
    defer wg107.Done()
    rwlock.Lock()
    time.Sleep(time.Millisecond * 10)
    rwlock.Unlock()
}

func test3() {
    start := time.Now()
    for i := 0; i < 10; i++ {
        wg107.Add(1)
        go write()
    }
    for i := 0; i < 100; i++ {
        wg107.Add(1)
        go read()
    }
    wg107.Wait()
    fmt.Println(time.Now().Sub(start))
}

func main() {
    test3()
}

执行：

111.770703ms