The fact that the sender may have to wait does not by itself make a "deadlock".
It's a deadlock if the sender blocks and, due to poor programming, the receiver is *never* ready to receive. That's a problem with your software, not with Go's concept of channels. Blocking on send until the channel is ready is exactly what is required normally. Are you suggesting something else should happen? If so, what exactly? This is well worth watching: Rethinking Classical Concurrency Patterns (Bryan C. Mills) https://www.youtube.com/watch?v=5zXAHh5tJqQ On Thursday, 14 April 2022 at 02:55:56 UTC+1 yan.z...@gmail.com wrote: > You are right, Brian. > The difference is not whether the channel is buffered or unbuffered - > while the receiver is present, none will encounter the deadlock. > > package main > > import ( > "fmt" > "time" > ) > > //var c = make(chan int) > var c = make(chan int, 2) > > func report(){ > for{ > select{ > case n:= <- c: > fmt.Println(n, time.Now().Format("2006-01-02 15:04:05")) > default: > time.Sleep(time.Second) > } > } > } > > func main() { > > go report() > > for i:=1; i<=5; i++{ > c <- i > } > > } > > But obviously, the buffered channel provides another layer of support in > case the receiver is temporarily absent: > > package main > > import ( > "fmt" > "time" > ) > > //var c = make(chan int) > var c = make(chan int, 5) > > func report(){ > for{ > select{ > case n:= <- c: > fmt.Println(n, time.Now().Format("2006-01-02 15:04:05")) > default: > time.Sleep(time.Second) > } > } > } > > func main() { > > for i:=1; i<=5; i++{ > c <- i > } > > report() > > } > > > > I made up a work around that just dumps the new message if the buffer is >> full: >> >> You don't need to do that: use select { ... } to check if the channel is >> ready to receive or not. >> https://go.dev/play/p/Mb7VVCTvnfk >> >> But in practice, this is almost never needed, because one goroutine is >> doing the sending and a different goroutine is doing the receiving. The >> sending goroutine blocks until the receiver is ready. >> >> On Wednesday, 13 April 2022 at 09:40:22 UTC+1 yan.z...@gmail.com wrote: >> >>> Since I found if inserting into a buffered channel could cause a crash >>> if it is full already >>> ( now I only use unbuffered channels in work) >>> https://groups.google.com/g/golang-nuts/c/U8lz6noKkuA >>> >>> package main >>> >>> var c = make(chan int, 1) >>> >>> func main() { >>> >>> c <- 1 >>> c <- 2 //fatal error: all goroutines are asleep - deadlock! >>> c <- 3 >>> >>> } >>> >>> I made up a work around that just dumps the new message if the buffer is >>> full: >>> >>> package main >>> >>> import ( >>> "fmt" >>> "sync" >>> ) >>> >>> type ChanInt struct{ >>> Ch chan int >>> Mu *sync.Mutex >>> } >>> >>> var c = ChanInt{make(chan int, 1), new(sync.Mutex)} >>> >>> func (ch ChanInt) Fill(k int){ >>> ch.Mu.Lock() >>> defer ch.Mu.Unlock() >>> >>> if len(ch.Ch) < cap(ch.Ch){ >>> ch.Ch <- k >>> } >>> } >>> >>> func main() { >>> >>> fmt.Println("Channel Status: ",len(c.Ch), cap(c.Ch)) >>> c.Fill(5) >>> fmt.Println("Channel Status: ", len(c.Ch), cap(c.Ch)) >>> fmt.Println("get one out of Channel:", <-c.Ch) >>> fmt.Println("Channel Status: ", len(c.Ch), cap(c.Ch)) >>> >>> c.Fill(6) >>> // c.Ch <- 7 //fatal error: all goroutines are asleep - deadlock! >>> c.Fill(7) >>> fmt.Println("Channel Status: ", len(c.Ch), cap(c.Ch)) >>> fmt.Println("get one out of Channel:", <-c.Ch) >>> } >>> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "golang-nuts" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/golang-nuts/6ExktXrF5Xc/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> golang-nuts...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/7df07f32-d7aa-45db-91d6-de75e18ad8d8n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/golang-nuts/7df07f32-d7aa-45db-91d6-de75e18ad8d8n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/0c91adbb-94c7-4475-891d-3c4bb3d4e80dn%40googlegroups.com.
