Thanks for this bit of history, Ian! I’ve been studying the memory model in grad school for a few years now and I think it’s well written. I was curious about how it came to be.
I think the “completes” also mater for buffered channels, for example: https://github.com/golang/go/issues/37355 <https://github.com/golang/go/issues/37355> Daniel > On 27 Nov 2020, at 23:46, Ian Lance Taylor <i...@golang.org> wrote: > > On Fri, Nov 27, 2020 at 12:57 PM Daniel Fava <danielsf...@gmail.com> wrote: >> >> Does anyone know how the Go memory model came to be? I don't have technical >> questions about it. I just would like to know the historical context. >> >> The model is specified in terms of happens-before, due to Lamport. But the >> following rule, which allows channels to be used as locks, was not part of >> Lamport's original formulation: >> >> "A receive from an unbuffered channel happens before the send on that >> channel completes. " >> >> I'm curious who (if anyone) was involved in including this rule. How did it >> come to be? >> >> I also find it fascinating how the word "completes" seems to make a world of >> difference. As I read it, removing the word "completes" from the rule above >> (and from the rule connecting a sender and its corresponding receiver >> receiver) would lead to a quite different memory model. I'm curious how >> intentional the "completes" is. > > As I recall, Tom Szymanski asked for the rules about when one > goroutine would see changes made by another goroutine, and how that > related to channel operations. Russ Cox described what he thought > should happen, Tom encouraged him to write that down, and Russ did, > winding up with > https://go.googlesource.com/go/+/82c38cf8dd628e6c90b6f1160be2a8d5088b77c9/doc/mem.html > (when reading that doc, remember that it was written in February, > 2009, and that the syntax has changed since then). > > The "completes" is intentional. A send/receive on an unbuffered > channel was always intended to serve as a synchronization point > between the goroutines. Otherwise it would be hard for different > goroutines to synchronize on anything. > > Ian -- 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/569DA3B6-9D3E-4D4E-8F76-2F8ABF546AE4%40gmail.com.
