为什么我的 Golang goroutine 代码会出现死锁？

huangapple
go评论106阅读模式
英文:

why my golang goroutine code get deadlocked

问题

我尝试使用通道和goroutine编写一些代码，但是出现了死锁，为什么会这样呢？我在使用WaitGroup方面有什么错误吗？我感到很困惑...

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"sync"
  6. )
  8. var wg sync.WaitGroup
  10. func main() {
  11. 	chan1 := make(chan string)
  12. 	chan2 := make(chan string)
  13. 	chan3 := make(chan string, 2)
  14. 	wg.Add(1)
  15. 	go makeChanStr("yeye", chan1, chan3)
  16. 	wg.Add(1)
  17. 	go makeChanStr("okok", chan2, chan3)
  18. 	wg.Wait()
  19. 	close(chan3)
  20. 	println(<-chan1)
  21. 	println(<-chan2)
  22. 	for chs := range chan3 {
  23. 		println(chs)
  24. 	}
  25. }
  27. func makeChanStr(s string, c1 chan string, c2 chan string) {
  28. 	defer wg.Done()
  30. 	c1 <- "get " + s
  31. 	c2 <- "same value"
  32. 	fmt.Printf("execute ok %s", s)
  33. }

Stackoverflow不让我提交问题......所以我只能添加一些文本.....

英文:

I try to write some goroutine with channel, but get deadlocked, why?
Am I doing wrong with WaitGroup, so confused...

  1. package main
  3. import (
  4.     &quot;fmt&quot;
  5.     &quot;sync&quot;
  6. )
  8. var wg sync.WaitGroup
  10. func main() {
  11.     chan1 := make(chan string)
  12.     chan2 := make(chan string)
  13. 	chan3 := make(chan string, 2)
  14.     wg.Add(1)
  15.     go makeChanStr(&quot;yeye&quot;, chan1, chan3)
  16.  	wg.Add(1)
  17. 	go makeChanStr(&quot;okok&quot;, chan2, chan3)
  18.     wg.Wait()
  19.     close(chan3)
  20.  	println(&lt;-chan1)
  21.     println(&lt;-chan2)
  22.     for chs := range chan3 {
  23. 	     println(chs)
  24.     }
  25. }
  27. func makeChanStr(s string, c1 chan string, c2 chan string) {
  28.     defer wg.Done()
  30.     c1 &lt;- &quot;get &quot; + s
  31. 	c2 &lt;- &quot;same value&quot;
  32. 	fmt.Printf(&quot;execute ok %s&quot;, s)
  33. }

Stackoverflow just don't let me submit the question.......so I just have to add some text.....

答案1

得分: 4

主要是在wg.Wait()的代码块上，它等待这两个goroutine完成（因为有wg.Add(1)和wg.Done()）。

  1. go makeChanStr("yeye", chan1, chan3)
  2. go makeChanStr("okok", chan2, chan3)

但它们在chan1（或chan2）上阻塞，因为它是一个无缓冲通道。

  1. chan1 := make(chan string)

尝试将chan1和chan2更改为带缓冲的通道：

  1. chan1 := make(chan string, 1)
  2. chan2 := make(chan string, 1)
英文:

main block on wg.Wait(), which wait this two go routines to finish(because of wg.Add(1) and wg.Done())

  1. go makeChanStr(&quot;yeye&quot;, chan1, chan3)
  2. go makeChanStr(&quot;okok&quot;, chan2, chan3)

but they block on chan1 (or chan2) , because it's an unbuffer channel.

  1. chan1 := make(chan string)

try change chan1 and chan2 to buffer channels:

  1. chan1 := make(chan string,1)
  2. chan2 := make(chan string,1)

答案2

得分: 1

这段代码在主goroutine中的wg.Wait()和工作goroutine中写入c1时会阻塞。为了避免这种情况，可以在wg.Wait()之前从c1和c2中读取数据，从而解除工作goroutine的阻塞，它们将不会在写入缓冲的c3时阻塞。结果是wg.Done()将被调用，wg.Wait()也不会阻塞主goroutine。

  1. package main
  3. import (
  4.     "fmt"
  5.     "sync"
  6. )
  8. var wg sync.WaitGroup
  10. func main() {
  11.     chan1 := make(chan string)
  12.     chan2 := make(chan string)
  13.     chan3 := make(chan string, 2)
  14.     wg.Add(1)
  15.     go makeChanStr("yeye", chan1, chan3)
  16.     wg.Add(1)
  17.     go makeChanStr("okok", chan2, chan3)
  18.     println(<-chan1)
  19.     println(<-chan2)
  20.     wg.Wait()
  21.     close(chan3)
  22.     for chs := range chan3 {
  23.          println(chs)
  24.     }
  25. }
  27. func makeChanStr(s string, c1 chan string, c2 chan string) {
  28.     defer wg.Done()
  30.     c1 <- "get " + s
  31.     c2 <- "same value"
  32.     fmt.Printf("execute %s\n", s)
  33. }
英文:

This code blocks on wg.Wait() in main goroutine and writing to c1 in workers. To avoid it - read from c1 and c2 prior to wg.Wait() thus unblock workers and they will not block on writing to buffered c3. As a result wg.Done() will be called and wg.Wait() will not block main goroutine as well.

  1. package main
  3. import (
  4.     &quot;fmt&quot;
  5.     &quot;sync&quot;
  6. )
  8. var wg sync.WaitGroup
  10. func main() {
  11.     chan1 := make(chan string)
  12.     chan2 := make(chan string)
  13.     chan3 := make(chan string, 2)
  14.     wg.Add(1)
  15.     go makeChanStr(&quot;yeye&quot;, chan1, chan3)
  16.     wg.Add(1)
  17.     go makeChanStr(&quot;okok&quot;, chan2, chan3)
  18.     println(&lt;-chan1)
  19.     println(&lt;-chan2)
  20.     wg.Wait()
  21.     close(chan3)
  22.     for chs := range chan3 {
  23.          println(chs)
  24.     }
  25. }
  27. func makeChanStr(s string, c1 chan string, c2 chan string) {
  28.     defer wg.Done()
  30.     c1 &lt;- &quot;get &quot; + s
  31.     c2 &lt;- &quot;same value&quot;
  32.     fmt.Printf(&quot;execute %s\n&quot;, s)
  33. }

huangapple
  • 本文由 发表于 2021年6月8日 21:27:31
  • 转载请务必保留本文链接：https://go.coder-hub.com/67887932.html
  • go
  • goroutine
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