英文:
Need run a goroutine for WaitGroup in a function
问题
我已经阅读了来自https://go.dev/blog/pipelines的一篇关于管道的文章。
我尝试移除覆盖**wg.Wait()**的goroutine，但结果导致所有的goroutine都处于休眠状态 - 死锁！
我真的不明白为什么会这样。
func merge(cs ...<-chan int) <-chan int {
var wg sync.WaitGroup
out := make(chan int)
// 为cs中的每个输入通道启动一个输出goroutine。output将值从c复制到out，直到c关闭，然后调用wg.Done。
output := func(c <-chan int) {
for n := range c {
out <- n
}
wg.Done()
}
wg.Add(len(cs))
for _, c := range cs {
go output(c)
}
// 启动一个goroutine，在所有输出goroutine完成后关闭out。这必须在wg.Add调用之后启动。
go func() {
wg.Wait()
close(out)
}()
return out
}
英文:
I've read a pipeline article from https://go.dev/blog/pipelines.
I've tried to remove the goroutine that covers wg.Wait() but it turns out that caused all goroutines are asleep - deadlock!
I really don't understand why.
func merge(cs ...<-chan int) <-chan int {
var wg sync.WaitGroup
out := make(chan int)
// Start an output goroutine for each input channel in cs. output
// copies values from c to out until c is closed, then calls wg.Done.
output := func(c <-chan int) {
for n := range c {
out <- n
}
wg.Done()
}
wg.Add(len(cs))
for _, c := range cs {
go output(c)
}
// Start a goroutine to close out once all the output goroutines are
// done. This must start after the wg.Add call.
go func() {
wg.Wait()
close(out)
}()
return out
}
答案1
得分: 1
out 是一个阻塞通道。你需要 return out 并让某个东西从 out 中消费，否则 output 协程在尝试写入任何内容时都会被阻塞。如果 merge 在消费者甚至有机会开始之前就等待等待组（即等待所有任务完成），那就是一个不可避免的死锁。
英文:
out is a blocking channel. You need to return out and let something consume from out, or else the output goroutines will block as soon as they try to write anything. If merge waits on the waitgroup (i.e. waits for everything to finish) before the consumer even has a chance to start, that's an inevitable deadlock.
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