But isn't this what is happening in the example? Or is write-only not sharing?
On Thu, 3 Aug 2017, 09:23 Dave Cheney, <d...@cheney.net> wrote: > IMO you need a lock whenever you are sharing a value between goroutines by > storing it in memory. > > On Thu, 3 Aug 2017, 17:21 Henrik Johansson <dahankz...@gmail.com> wrote: > >> I think I am mostly after a mental pattern to easily recognise when >> synchronizations are needed. >> >> I am decently good at this but I tend to be very conservative and use >> locks and atomics perhaps when they are not needed. >> But here we have several goroutines all taking part in the initialisation >> itself concurrently writing to the same array. How can this be safe in >> light of https://golang.org/ref/mem#tmp_10 . I get that your comment >> about "happens before" comes in here if there were any readers but >> eventually there will be readers or we would never need to do this. If the >> main after some time wants to access these values is it enough to make sure >> the goroutines are done perhaps using a WaitGroup or do we have to use some >> other synchronisation to ensure the visibility of the data in the array? >> >> https://play.golang.org/p/8BfrPhyIEb >> >> Or is it needed to do something like this: >> >> https://play.golang.org/p/9QgTP5Dqc7 >> >> I mean aside from the poor form of sleeping like this, the idea is to >> simulate usage "at some point later in time". >> >> It gets hypothetical pretty quick and usually when this happens I make >> sure to create a new array/slice/whatever and then atomically swap it >> before some other goroutine uses it but I generally avoid indexing >> assignment from go routines like this even though it seems to be ok. >> >> Does this hold for slices as well as for arrays? What about assignments >> to fields in structs? Can several goroutines safely write to different >> fields in the same struct assuming they are word sized? Does this hold for >> all architectures? >> >> I am sorry if I am still a bit unclear but I find it hard to ask properly >> when I am a bit unsure of the topic. :D >> >> >> >> tors 3 aug. 2017 kl 07:49 skrev Dave Cheney <d...@cheney.net>: >> >>> I'm not really sure what you are asking. I think your second paragraph >>> got eaten by autocorrect at the critical point. Could try maybe asking your >>> question in a different way? >> >> >>> >>> -- >>> 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.
