Using atomic operations, cache consistency will cause some threads to endless loop?

Technical Discussion
1

When I use the following test code, some threads will loop. But we added println() os.Creat () or os.Open (), this will not happen。

	var casValue = new(int64)
	*casValue = 0
	var old int64 = 0
	var new int64 = 1
	var container *list.List
	container = list.New()
	var wg sync.WaitGroup
	wg.Add(10)
	t1 := time.Now()
	for i := 0; i < 10; i++ {
		go func(i int) {
			for j := 0; j < 10000; {
				if atomic.CompareAndSwapInt64(casValue, old, new) {
					var test = "hello world，hello world，hello world"
					container.PushBack(test)
					*casValue = 0
					j++
				}
				//println("hello")、os.Create("test")、os.Open("test") will solve this problem
			}
			println("casValue=", *casValue)
			wg.Done()
		}(i)
	}
	lentcy := time.Since(t1)
	wg.Wait()
	fmt.Println(container.Len())
2

You have a data race, Therefore, your results are undefined.

Go: Data Race Detector

package main

import (
	"container/list"
	"fmt"
	"sync"
	"sync/atomic"
	"time"
)

func main() {

	var casValue = new(int64)
	*casValue = 0
	var old int64 = 0
	var new int64 = 1
	var container *list.List
	container = list.New()
	var wg sync.WaitGroup
	wg.Add(10)
	t1 := time.Now()
	for i := 0; i < 10; i++ {
		go func(i int) {
			for j := 0; j < 10000; {
				if atomic.CompareAndSwapInt64(casValue, old, new) {
					var test = "hello world，hello world，hello world"
					container.PushBack(test)
					*casValue = 0
					j++
				}
				//println("hello")、os.Create("test")、os.Open("test") will solve this problem
			}
			println("casValue=", *casValue)
			wg.Done()
		}(i)
	}
	wg.Wait()
	latency := time.Since(t1)
    fmt.Println(latency)
	fmt.Println(container.Len())

}

.

$ go run -race racer.go
==================
WARNING: DATA RACE
Write at 0x00c00013a010 by goroutine 8:
  sync/atomic.CompareAndSwapInt64()
      /home/peter/go/src/runtime/race_amd64.s:327 +0xb
  main.main.func1()
      /home/peter/Sync/gopath/mod/gf/racer.go:25 +0x84

Previous write at 0x00c00013a010 by goroutine 7:
  main.main.func1()
      /home/peter/Sync/gopath/mod/gf/racer.go:28 +0x312

Goroutine 8 (running) created at:
  main.main()
      /home/peter/Sync/gopath/mod/gf/racer.go:23 +0x23d

Goroutine 7 (running) created at:
  main.main()
      /home/peter/Sync/gopath/mod/gf/racer.go:23 +0x23d
==================
==================
WARNING: DATA RACE
Read at 0x00c000124158 by goroutine 9:
  container/list.(*List).PushBack()
      /home/peter/go/src/container/list/list.go:155 +0x104
  main.main.func1()
      /home/peter/Sync/gopath/mod/gf/racer.go:27 +0x93

Previous write at 0x00c000124158 by goroutine 7:
  container/list.(*List).insert()
      /home/peter/go/src/container/list/list.go:96 +0x27c
  container/list.(*List).insertValue()
      /home/peter/go/src/container/list/list.go:104 +0x113
  container/list.(*List).PushBack()
      /home/peter/go/src/container/list/list.go:155 +0xf5
  main.main.func1()
      /home/peter/Sync/gopath/mod/gf/racer.go:27 +0x93

Goroutine 9 (running) created at:
  main.main()
      /home/peter/Sync/gopath/mod/gf/racer.go:23 +0x23d

Goroutine 7 (running) created at:
  main.main()
      /home/peter/Sync/gopath/mod/gf/racer.go:23 +0x23d
==================
<SNIP>
4

When I cancel the println (“hello”) annotation, there is no data conflict. What’s the reason?

5

Go version is upgraded from 1.13.5 to 1.14.1, and the problem is solved，thank you very much！

6

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