Goroutine与Mutex的同步

huangapple
go评论104阅读模式
英文:

Goroutine synchronization with Mutex

问题

  1. var n int32 = 0
  2. var mutex *sync.Mutex = new(sync.Mutex)
  4. for i := 0; i < 100000; i++ {
  5. 	go func() {
  6. 		mutex.Lock()
  7. 		defer mutex.Unlock()
  8. 		atomic.AddInt32(&n, 1)
  9. 	}()
  10. }
  12. fmt.Println(n)

我想知道为什么 n 的结果不是 100000，看起来互斥锁没有起作用。

英文: 
  1.     var n int32 = 0
  2. 	var mutex *sync.Mutex = new(sync.Mutex)
  4. 	for i := 0; i &lt; 100000; i++ {
  5. 		go func() {
  6. 			mutex.Lock()
  7. 			defer mutex.Unlock()
  8. 			atomic.AddInt32(&amp;n, 1)
  10. 		}()
  11. 	}
  13. 	fmt.Println(n)

I'm wondering why the result of n is not 100000, looks like the mutex lock does not work.

答案1

得分: 2

fmt.Println(n)在go线程完成之前执行，你需要在fmt.Println(n)之前添加time.Sleep(5 * time.Millisecond)，如下所示：

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"sync"
  6. 	"sync/atomic"
  7. 	"time"
  8. )
  10. func main() {
  11. 	var n int32 = 0
  12. 	var mutex *sync.Mutex = new(sync.Mutex)
  14. 	for i := 0; i < 100000; i++ {
  15. 		go func() {
  16. 			mutex.Lock()
  17. 			defer mutex.Unlock()
  18. 			atomic.AddInt32(&n, 1)
  20. 		}()
  21. 	}
  22. 	time.Sleep(5 * time.Millisecond)
  23. 	fmt.Println(n)
  24. }

输出：

100000

或者

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"sync"
  6. 	"sync/atomic"
  7. )
  9. func main() {
  10. 	var n int32 = 0
  11. 	var mutex *sync.Mutex = new(sync.Mutex)
  12. 	var wg sync.WaitGroup
  14. 	for i := 0; i < 100000; i++ {
  15. 		wg.Add(1)
  16. 		go func() {
  17. 			mutex.Lock()
  18. 			defer mutex.Unlock()
  19. 			atomic.AddInt32(&n, 1)
  20. 			wg.Done()
  22. 		}()
  23. 	}
  24. 	wg.Wait()
  25. 	fmt.Println(n)
  26. }
  28. 输出：
  29. --------
  30. 100000
英文:

fmt.Println(n) is executing before the go threads completion,You need to add the time.Sleep(5 * time.Millisecond) before fmt.Println(n) like below

  1.    package main
  2.     
  3.     import (
  4.     	&quot;fmt&quot;
  5.     	&quot;sync&quot;
  6.     	&quot;sync/atomic&quot;
  7.     	&quot;time&quot;
  8.     )
  9.     
  10.     func main() {
  11.     	var n int32 = 0
  12.     	var mutex *sync.Mutex = new(sync.Mutex)
  13.     
  14.     	for i := 0; i &lt; 100000; i++ {
  15.     		go func() {
  16.     			mutex.Lock()
  17.     			defer mutex.Unlock()
  18.     			atomic.AddInt32(&amp;n, 1)
  19.     
  20.     		}()
  21.     	}
  22.     	time.Sleep(5 * time.Millisecond)
  23.     	fmt.Println(n)
  24.     }
  25. Output :
  26. --------
  27. 100000

Or

  1. package main
  3. import (
  4. 	&quot;fmt&quot;
  5. 	&quot;sync&quot;
  6. 	&quot;sync/atomic&quot;
  7. )
  9. func main() {
  10. 	var n int32 = 0
  11. 	var mutex *sync.Mutex = new(sync.Mutex)
  12. 	var wg sync.WaitGroup
  14. 	for i := 0; i &lt; 100000; i++ {
  15. 		wg.Add(1)
  16. 		go func() {
  17. 			mutex.Lock()
  18. 			defer mutex.Unlock()
  19. 			atomic.AddInt32(&amp;n, 1)
  20. 			wg.Done()
  22. 		}()
  23. 	}
  24. 	wg.Wait()
  25. 	fmt.Println(n)
  26. }
  28. Output :
  29. --------
  30. 100000

huangapple
  • 本文由 发表于 2022年9月22日 12:40:56
  • 转载请务必保留本文链接：https://go.coder-hub.com/73809431.html
  • go
  • goroutine
  • mutex
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