dateraces.md

description
golang 数据争用date races

数据争用

定义：

① 多个线程对于同一个变量、

② 同时地、

③ 进行读/写操作的现象并且

④ 至少有一个线程进行写操作。

（也就是说，如果所有线程都是只进行读操作，那么将不构成数据争用） 后果：如果发生了数据争用，读取该变量时得到的值将变得不可知，使得该多线程程序的运行结果将完全不可预测，可能直接崩溃。 如何防止：对于有可能被多个线程同时访问的变量使用排他访问控制，具体方法包括使用mutex（互斥量）和monitor（监视器），或者使用atomic变量。

golang date races

Data races are among the most common and hardest to debug types of bugs in concurrent systems. A data race occurs when two goroutines access the same variable concurrently and at least one of the accesses is a write. See the The Go Memory Model for details.

Here is an example of a data race that can lead to crashes and memory corruption:

func main() {
    c := make(chan bool)
    m := make(map[string]string)
    go func() {
        m["1"] = "a" // First conflicting access.
        c <- true
    }()
    m["2"] = "b" // Second conflicting access.
    <-c
    for k, v := range m {
        fmt.Println(k, v)
    }
}

执行 go run -race test.go

执行结果

==================
WARNING: DATA RACE
Write at 0x00c420092180 by goroutine 6:
  runtime.mapassign_faststr()
      /usr/local/go/src/runtime/hashmap_fast.go:694 +0x0
  main.main.func1()
      /Downloads/test/test/test.go:20 +0x5d

Previous write at 0x00c420092180 by main goroutine:
  runtime.mapassign_faststr()
      /usr/local/go/src/runtime/hashmap_fast.go:694 +0x0
  main.main()
      /Downloads/test/test/test.go:23 +0xc9

Goroutine 6 (running) created at:
  main.main()
      /Downloads/test/test/test.go:19 +0x9a
==================
2 b
1 a
Found 1 data race(s)
exit status 66