Go并发编程实现数据竞争

目录

• 1.前言
• 2.数据竞争

• 2.1 示例一
• 2.2 循环中使用goroutine引用临时变量
• 2.3 引起变量共享
• 2.4 不受保护的全局变量
• 2.5 未受保护的成员变量
• 2.6 接口中存在的数据竞争

go test -race main.go
go build -race

package main
import (
 "fmt"
 "sync"
)
var wg sync.WaitGroup
var counter int
func main() {
 // 多跑几次来看结果
 for i := 0; i < 100000; i++ {
  run()
 }
 fmt.Printf("Final Counter: %d\n", counter)
}
func run() {
    // 开启两个 协程，操作
 for i := 1; i <= 2; i++ {
  wg.Add(1)
  go routine(i)
 }
 wg.Wait()
}
func routine(id int) {
 for i := 0; i < 2; i++ {
  value := counter
  value++
  counter = value
 }
 wg.Done()
}

go run -race ./main.go

GORACE="option1=val1 option2=val2"

GORACE="halt_on_error=1 strip_path_prefix=/mnt/d/gopath/src/Go_base/daily_test/data_race/01_data_race" go run -race ./demo.go

func main() {
 var wg sync.WaitGroup
 wg.Add(5)
 for i := 0; i < 5; i++ {
  go func() {
   fmt.Println(i) 
   wg.Done()
  }()
 }
    wg.Wait()
}

func main() {
 var wg sync.WaitGroup
 wg.Add(5)
 for i := 0; i < 5; i++ {
  go func(i int) {
   fmt.Println(i)
   wg.Done()
  }(i)
 }
 wg.Wait()
}

package main
import "os"
func main() {
 ParallelWrite([]byte("xxx"))
}
// ParallelWrite writes data to file1 and file2, returns the errors.
func ParallelWrite(data []byte) chan error {
 res := make(chan error, 2)
 // 创建/写入第一个文件
 f1, err := os.Create("/tmp/file1")
 if err != nil {
  res <- err
 } else {
  go func() {
   // 下面的这个函数在执行时，是使用err进行判断，但是err的变量是个共享的变量
   _, err = f1.Write(data)
   res <- err
   f1.Close()
  }()
 }
  // 创建写入第二个文件n
 f2, err := os.Create("/tmp/file2")
 if err != nil {
  res <- err
 } else {
  go func() {
   _, err = f2.Write(data)
   res <- err
   f2.Close()
  }()
 }
 return res
}

root@failymao:/mnt/d/gopath/src/Go_base/daily_test/data_race# go run -race demo2.go
==================
WARNING: DATA RACE
Write at 0x00c0001121a0 by main goroutine:
  main.ParallelWrite()
      /mnt/d/gopath/src/Go_base/daily_test/data_race/demo2.go:28 +0x1dd
  main.main()
      /mnt/d/gopath/src/Go_base/daily_test/data_race/demo2.go:6 +0x84
Previous write at 0x00c0001121a0 by goroutine 7:
  main.ParallelWrite.func1()
      /mnt/d/gopath/src/Go_base/daily_test/data_race/demo2.go:21 +0x94
Goroutine 7 (finished) created at:
  main.ParallelWrite()
      /mnt/d/gopath/src/Go_base/daily_test/data_race/demo2.go:19 +0x336
  main.main()
      /mnt/d/gopath/src/Go_base/daily_test/data_race/demo2.go:6 +0x84
==================
Found 1 data race(s)
exit status 66

_, err := f1.Write(data)
...
_, err := f2.Write(data)
...

// 定义一个全局变量 map数据类型
var service = map[string]string{}
// RegisterService RegisterService
// 用于写入或更新key-value
func RegisterService(name, addr string) {
 service[name] = addr
}
// LookupService LookupService
// 用于查询某个key-value
func LookupService(name string) string {
 return service[name]
}

var (
service   map[string]string
serviceMu sync.Mutex
)
func RegisterService(name, addr string) {
 serviceMu.Lock()
 defer serviceMu.Unlock()
 service[name] = addr
}
func LookupService(name string) string {
 serviceMu.Lock()
 defer serviceMu.Unlock()
 return service[name]
}

type Watchdog struct{ 
    last int64
}
func (w *Watchdog) KeepAlive() {
    // 第一次进行赋值操作
 w.last = time.Now().UnixNano() 
}
func (w *Watchdog) Start() {
 go func() {
  for {
   time.Sleep(time.Second)
   // 这里在进行判断的时候，很可能w.last更新正在进行
   if w.last < time.Now().Add(-10*time.Second).UnixNano() {
    fmt.Println("No keepalives for 10 seconds. Dying.")
    os.Exit(1)
   }
  }
 }()
}

type Watchdog struct{ 
    last int64 
}
func (w *Watchdog) KeepAlive() {
    // 修改或更新
 atomic.StoreInt64(&w.last, time.Now().UnixNano())
}
func (w *Watchdog) Start() {
 go func() {
  for {
   time.Sleep(time.Second)
   // 读取
   if atomic.LoadInt64(&w.last) < time.Now().Add(-10*time.Second).UnixNano() {
    fmt.Println("No keepalives for 10 seconds. Dying.")
    os.Exit(1)
   }
  }
 }()
}

package main
import "fmt"
type IceCreamMaker interface {
 // Great a customer.
 Hello()
}
type Ben struct {
 name string
}
func (b *Ben) Hello() {
 fmt.Printf("Ben says, \"Hello my name is %s\"\n", b.name)
}
type Jerry struct {
 name string
}
func (j *Jerry) Hello() {
 fmt.Printf("Jerry says, \"Hello my name is %s\"\n", j.name)
}
func main() {
 var ben = &Ben{name: "Ben"}
 var jerry = &Jerry{"Jerry"}
 var maker IceCreamMaker = ben
 var loop0, loop1 func()
 loop0 = func() {
  maker = ben
  go loop1()
 }
 loop1 = func() {
  maker = jerry
  go loop0()
 }
 go loop0()
 for {
  maker.Hello()
 }
}

type interface struct {
   Type uintptr     // points to the type of the interface implementation
   Data uintptr     // holds the data for the interface's receiver
}