RWMutex 读写互斥锁

基本原则:

1.可以随便读，多个goroutine同时读
2.写的时候，啥也不能干，不能读也不能写

RWMutex四个方法:

func(*RWMutex)Lock //写锁定

func(*RWMutex)Unlock //写锁定

func(*RWMutex)RLock //读锁定

func(*RWMutex)RUnlock //读解锁

一、随便读

package main

import (
    "sync"
    "time"
)

var m *sync.RWMutex

func main() {
    m = new(sync.RWMutex)

    //多个同时读
    go read(1)
    go read(2)

    time.Sleep(2*time.Second)
}

func read(i int) {
    println(i, "read start")

    m.RLock()
    println(i, "reading")
    time.Sleep(1*time.Second)
    m.RUnlock()

    println(i,"read over")
}

result:

1 read start
1 reading
2 read start
2 reading
1 read over
2 read over

二、写的时候啥也不能干

package main

import (
    "sync"
    "time"
)

var m *sync.RWMutex

func main() {
    m = new(sync.RWMutex)

    // 写的时候啥也不能干
    go write(1)
    go read(2)
    go write(3)

    time.Sleep(2*time.Second)
}

func read(i int) {
    println(i, "read start")

    m.RLock()
    println(i, "reading")
    time.Sleep(1*time.Second)
    m.RUnlock()

    println(i, "read over")
}

func write(i int) {
    println(i, "write start")

    m.Lock()
    println(i, "writing")
    time.Sleep(1*time.Second)
    m.Unlock()

    println(i, "write over")
}

result:

1 write start
1 writing
2 read start
3 write start
1 writing over
2 reading
2 read over
3 writing
3 writing over