为什么所有goroutine都在睡觉-死锁。 识别瓶颈

Question

package main

import (
    "fmt"
    "runtime"
    "sync"
    "time"
)

func main() {
    intInputChan := make(chan int, 50)
    var wg sync.WaitGroup
    for i := 0; i < 3; i++ {
        wg.Add(1)
        go worker(intInputChan, wg)
    }
    for i := 1; i < 51; i++ {
        fmt.Printf("Inputs. %d 
", i)
        intInputChan <- i
    }
    close(intInputChan)
    wg.Wait()
    fmt.Println("Existing Main App... ")
    panic("---------------")
}

func worker(input chan int, wg sync.WaitGroup) {
    defer func() {
        fmt.Println("Executing defer..")
        wg.Done()
    }()

    for {
        select {
        case intVal, ok := <-input:
            time.Sleep(100 * time.Millisecond)
            if !ok {
                input = nil
                return
            }
            fmt.Printf("%d  %v
", intVal, ok)

        default:
            runtime.Gosched()
        }
    }

}

error thrown is.

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [semacquire]: sync.(*WaitGroup).Wait(0xc082004600) c:/go/src/sync/waitgroup.go:132 +0x170 main.main() E:/Go/go_projects/go/src/Test.go:22 +0x21a

Answer 1

I just tried it (playground) passing a wg *sync.WaitGroup and it works.

Passing sync.WaitGroup means passing a copy of the sync.WaitGroup (passing by value): the goroutine mentions Done() to a different sync.WaitGroup.

var wg sync.WaitGroup
for i := 0; i < 3; i++ {
    wg.Add(1)
    go worker(intInputChan, &wg)
}

Note the &wg: you are passing by value the pointer to the original sync.WaitGroup, for the goroutine to use.