go - 如何修复 "one problem on race condition check which using go-build-race tools"？

Question

起初，我知道代码有一些竞争条件，所以我使用“go build -race”命令来检查它，我想看看结果如何显示，当我第一次运行时，它显示了第一个结果如下，然后再次运行显示第二个，它有两个不同的结果，我不知道为什么，有谁能告诉我原因，以及代码是如何执行的？，非常感谢很多。

源代码:

package main

import (
    "fmt"
    "runtime"
    "sync"
)

var (
    counter int
    wg sync.WaitGroup
)

func main() {
    wg.Add(2)

    go incCounter(1)
    go incCounter(2)

    wg.Wait()

    fmt.Println("Final Counter:", counter)

}

func incCounter(id int) {
    defer wg.Done()

    for count := 0; count < 2; count++ {
        value := counter
        // switch goroutine
        runtime.Gosched()
        value++
        counter = value
    }
}

当我使用 go build -race 工具检查竞争条件时，它显示了两个不同的结果，如下所示:

一个结果:

==================
WARNING: DATA RACE
Write at 0x0000005fb2d0 by goroutine 7:
  main.incCounter()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:34 +0x97

Previous read at 0x0000005fb2d0 by goroutine 6:
  main.incCounter()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:30 +0x76

Goroutine 7 (running) created at:
  main.main()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:18 +0x90

Goroutine 6 (running) created at:
  main.main()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:17 +0x6f
==================
==================
WARNING: DATA RACE
Write at 0x0000005fb2d0 by goroutine 6:
  main.incCounter()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:34 +0x97

Previous write at 0x0000005fb2d0 by goroutine 7:
  main.incCounter()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:34 +0x97

Goroutine 6 (running) created at:
  main.main()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:17 +0x6f

Goroutine 7 (running) created at:
  main.main()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:18 +0x90
==================
Final Counter: 2
Found 2 data race(s)

第二个结果:

==================
WARNING: DATA RACE
Read at 0x0000005fb2d0 by goroutine 7:
  main.incCounter()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:30 +0x76

Previous write at 0x0000005fb2d0 by goroutine 6:
  main.incCounter()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:34 +0x97

Goroutine 7 (running) created at:
  main.main()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:18 +0x90

Goroutine 6 (finished) created at:
  main.main()
      D:/Go/projects/hello-world/src/concurrency/list7/m.go:17 +0x6f
==================
Final Counter: 4
Found 1 data race(s)

它们是两个不同的结果。

Answer 1

我建议你探索 go 中的调度(来自 ardanlabs 的好文章)。

简短的回答是你无法控制执行顺序，go runtime 可以。同一个程序的每次执行都不会产生相同的执行轨迹。 Race detector跟踪每次运行的“活泼”行为，结果直接取决于调度程序的决定。