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.
