Thanks, I should have checked the spec. On Thu, Sep 1, 2016 at 11:14 AM Darren Hoo <darren....@gmail.com> wrote:
> I don't think so. > > see https://golang.org/ref/spec#Select_statements > > If one or more of the communications can proceed, a single one that can > proceed is chosen via a uniform pseudo-random selection. Otherwise, if > there is a default case, that case is chosen. > > So if the done channel has been sent, the first case will be selected and > f will not be called anymore. > > On Friday, September 2, 2016 at 1:58:04 AM UTC+8, freeformz wrote: > >> I think you can still deadlock, but I'm not sure if the `default:` case >> is considered for random selection of a select like other branches are. It >> would just be less deterministic. >> >> On Thu, Sep 1, 2016 at 10:38 AM Darren Hoo <darre...@gmail.com> wrote: >> >>> Got it, using buffered channel works for me >>> >>> ints := make(chan int, 1) >>> done := make(chan bool, 1) >>> >>> go func() { >>> for i := 0; i < 100; i++ { >>> ints <- i >>> } >>> close(ints) >>> }() >>> >>> f := func() { >>> j := 0 >>> for { >>> i, ok := <-ints >>> if !ok { >>> done <- true >>> return >>> } >>> j++ >>> >>> fmt.Println(i) >>> >>> //10 ints for one batch >>> if j == 10 { >>> return >>> } >>> } >>> } >>> >>> exit: >>> for { >>> f() >>> >>> select { >>> case <-done: >>> fmt.Println("Exiting") >>> break exit >>> default: >>> //do nothing just next f() >>> } >>> } >>> >>> >>> >>> On Friday, September 2, 2016 at 1:30:10 AM UTC+8, freeformz wrote: >>> >>>> If you execute it you are told on which lines the deadlock happens... >>>> >>>> fatal error: all goroutines are asleep - deadlock! >>>> >>>> goroutine 1 [chan send]: >>>> main.main.func2() >>>> /Users/emuller/go/src/github.com/freeformz/tt/main.go:25 +0xce >>>> main.main() >>>> /Users/emuller/go/src/github.com/freeformz/tt/main.go:37 +0x118 >>>> exit status 2 >>>> >>>> main.go:25 is the line that says `done <- true`. >>>> >>>> The `done` channel isn't buffered and the first loop through will >>>> select that path, but there is not another goroutine selecting from done. >>>> so f() never returns. Deadlock. >>>> >>>> On Thu, Sep 1, 2016 at 10:04 AM Darren Hoo <darre...@gmail.com> wrote: >>>> >>> var wg sync.WaitGroup >>>>> >>>>> ints := make(chan int, 1) >>>>> done := make(chan bool) >>>>> >>>>> go func() { >>>>> for i := 0; i < 3; i++ { >>>>> ints <- i >>>>> } >>>>> close(ints) >>>>> }() >>>>> >>>>> f := func() { >>>>> wg.Add(1) >>>>> defer wg.Done() >>>>> >>>>> for { >>>>> i, ok := <-ints >>>>> if !ok { >>>>> done <- true >>>>> return >>>>> } >>>>> } >>>>> } >>>>> >>>>> exit: >>>>> for { >>>>> select { >>>>> case <-done: >>>>> break exit >>>>> default: >>>>> f() >>>>> } >>>>> } >>>>> wg.Wait() >>>>> >>>>> >>>>> >>>>> -- >>>>> 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...@googlegroups.com. >>>> >>>> >>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>> -- >>> 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...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- > 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. > For more options, visit https://groups.google.com/d/optout. > -- 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. For more options, visit https://groups.google.com/d/optout.
