Go語言並發編程 互斥鎖詳情

package main

import (
 "flag"
 "fmt"
 "sync"
)

var (
    mutex   sync.Mutex
    balance int
    protecting uint  // 是否加鎖
    sign = make(chan struct{}, 10) //通道，用於等待所有goroutine
)

// 存錢
func deposit(value int) {
    defer func() {
        sign <- struct{}{}
    }()

    if protecting == 1 {
        mutex.Lock()
        defer mutex.Unlock()
    }

    fmt.Printf("餘額: %d\n", balance)
    balance += value
    fmt.Printf("存 %d 後的餘額: %d\n", value, balance)
    fmt.Println()

}

// 取錢
func withdraw(value int) {
    defer func() {
        sign <- struct{}{}
    }()
    
    if protecting == 1 {
        mutex.Lock()
        defer mutex.Unlock()
    }

    fmt.Printf("餘額: %d\n", balance)
    balance -= value
    fmt.Printf("取 %d 後的餘額: %d\n", value, balance)
    fmt.Println()

}

func main() {
    
    for i:=0; i < 5; i++ {
        go withdraw(500) // 取500
        go deposit(500)  // 存500
    }

    for i := 0; i < 10; i++ {
  <-sign
 }
    fmt.Printf("當前餘額: %d\n", balance)
}

func init() {
    balance = 1000 // 初始賬戶餘額為1000
    flag.UintVar(&protecting, "protecting", 0, "是否加鎖，0表示不加鎖，1表示加鎖")
}

package main

import (
 "fmt"
 "sync"
)

// account 代表計數器。
type account struct {
 num uint         // 操作次數
 balance int   // 餘額
 rwMu  *sync.RWMutex // 讀寫鎖
}

var sign = make(chan struct{}, 15) //通道，用於等待所有goroutine

// 查看餘額：使用讀鎖
func (c *account) check() {
 defer func() {
        sign <- struct{}{}
    }()
 c.rwMu.RLock()
 defer c.rwMu.RUnlock()
 fmt.Printf("%d 次操作後的餘額: %d\n", c.num, c.balance)
}

// 存錢：寫鎖
func (c *account) deposit(value int) {
 defer func() {
        sign <- struct{}{}
    }()
    c.rwMu.Lock()
 defer c.rwMu.Unlock() 

 fmt.Printf("餘額: %d\n", c.balance)   
 c.num += 1
    c.balance += value
    fmt.Printf("存 %d 後的餘額: %d\n", value, c.balance)
    fmt.Println() 
}

// 取錢：寫鎖
func (c *account) withdraw(value int) {
    defer func() {
        sign <- struct{}{}
    }()
 c.rwMu.Lock()
 defer c.rwMu.Unlock()   
 fmt.Printf("餘額: %d\n", c.balance)     
 c.num += 1
    c.balance -= value
 fmt.Printf("取 %d 後的餘額: %d\n", value, c.balance)
    fmt.Println()  
}


func main() {
 c := account{0, 1000, new(sync.RWMutex)}

 for i:=0; i < 5; i++ {
        go c.withdraw(500) // 取500
        go c.deposit(500)  // 存500
  go c.check()
    }

    for i := 0; i < 15; i++ {
  <-sign
 }
 fmt.Printf("%d 次操作後的餘額: %d\n", c.num, c.balance)

}