dqrq93879 2019-09-13 01:21
浏览 37
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进入例行程序,出现通道死锁

I just started to learn Go so please bear with me, I've tried to play around with Go routines and channels but are getting a deadlock somehow.

Here's the example

package main

import (
    "fmt"
    "sync"
)


func main() {
    total := 2
    var wg sync.WaitGroup
    wg.Add(total)

    ch := make(chan int)

    for idx := 0; idx < total; idx++ {
        fmt.Printf("Processing idx %d
", idx)

        go func(idx int) {
            defer wg.Done()
            ch <- idx
        }(idx)
    }

    for val := range ch {
        fmt.Println(val)
    }

    fmt.Println("Wait")
    wg.Wait()
}

which throws the error

Processing idx 0
Processing idx 1
1
0
fatal error: all goroutines are asleep - deadlock!
  • 写回答

1条回答 默认 最新

  • dpv21589 2019-09-13 01:44
    关注

    range ch reads from the channel until it is closed.

    How many times do you call close(ch)? When will the for val := range ch loop terminate?


    When should you close the channel? You have a lot of options here, but one way to do it is to add another goroutine:

    go func() {
        wg.Wait()
        close(ch)
    }()
    

    e.g., after spinning off all routines that will write-to-channel-then-call-wg.Done(), so that the channel is closed once all the writers are done writing. (You can run this goroutine as soon as you've increased the wg count to account for all writers.)

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

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