使用带有选择的通道时的 Goroutine 死锁

Question

我试图重写一个没有使用select 或WaitGroup 的工作程序，以便它可以实现select 和WaitGroup，但我遇到了一个问题，我可以找不到解决办法。看来goroutine死锁了，因为Manager函数没有从writer通道取数据，所以通道被阻塞发送/接收，程序被锁住了。

原来工作的Manager函数，没有select：

func Manager(list *[]Request, writerChan <-chan int) {
    ageIn, writersOpen := <-writerChan
    for {
        if writersOpen { // if writers channel is open

            Add(list, Request{Value: ageIn, Count: 1}) // putting new object to list
            ageIn, writersOpen = <-writerChan          // receiving new player from writer channe;

        } else {
            break
        }
    }
}

所以我有一个工作程序，但需要实现WaitGroup 和select，有更新的代码：

更新了Manager 函数，实现select：

func Manager(list *[]Request, writerChan <-chan int) {
    defer waitGroup.Done()
    for {
        select {
        case ageIn := <-writerChan:
            Add(list, Request{Value: ageIn, Count: 1}) // add player to list
        default:
            break
        }
    }
}

更新了Main 函数，实现WaitGroup：

var waitGroup sync.WaitGroup

func main() {
    list := ParallelList{List: make([]Request, 0)}
    readers, teams, players := ReadData("data.txt")
    writerChan := make(chan int)          //any2one writers channel
    writerFinishChan := make(chan int, 6) // channel to know when all writers are done writing

    waitGroup.Add(6)

    for i := 0; i < len(teams); i++ {
        go Writer(teams, teams[i], writerChan, writerFinishChan)
    }

    go Manager(&list.List, writerChan)
    waitGroup.Wait()
}

Writer 函数向 writerChan 发送数据

func Writer(teams [][]Player, team []Player, writerChan chan<- int,
    writerFinishChan chan int) {
    defer waitGroup.Done()
    count := len(team)
    for i := 0; i < count; i++ {
        writerChan <- team[i].Age
    }
    writerFinishChan <- 1 // when writer finishes writing, he puts 1 to the "writerFinishChan"

    if len(writerFinishChan) == len(teams) { // if all writers are done writing (the len should be equal to 6)
        close(writerChan)
    }
}

所以现在的问题是，在实现select 和WaitGroup 之后，我的程序不再正常工作，它给了我一个“致命错误：goroutines 睡着了，死锁”。

也许有人可以帮我解决这个问题？我很确定问题出在Manager 函数中，它是select 块

Answer 1

看起来您退出Manager 函数的逻辑现在不同了。在您等待频道关闭之前，现在您根本不检查。事实上Manager 永远不会退出。这也意味着WaitGroup 永远不会完成。

我认为Manager 中的选择没有必要。如果您要关闭通道，则只需覆盖它：

for ageIn := range writerChan {
  Add(list, Request{Value: ageIn, Count: 1}) // putting new object to list
}

writerChan 关闭时，这将正确退出。