On Mon, Jan 6, 2020 at 5:47 PM hao dong <hao.a.d...@gmail.com> wrote:
> thanks for your reply. Could you guide me any readings or source code > about channel of happens before. > I think you have misunderstood this text in the https://golang.org/ref/mem document you linked to: Within a single goroutine, reads and writes must behave as if they executed > in the order specified by the program. That is, compilers and processors > may reorder the reads and writes executed within a single goroutine only > when the reordering does not change the behavior within that goroutine as > defined by the language specification. Because of this reordering, the > execution order observed by one goroutine may differ from the order > perceived by another. The send on the channel is not a "write" operation in the sense meant by the above text. Nor is the receive on the channel a "read" operation. That paragraph is talking about reads and writes of memory in units (bytes, words, etc.) supported by the CPU. Also, notice the "only when the reordering does not change the behavior" portion of the above text. If the compiler did the assignment after the send on the channel that would change the behavior of the program. Channel ops are what are known as memory barriers, and thus don't allow ops before or after the channel op to be reordered before or after the op. -- Kurtis Rader Caretaker of the exceptional canines Junior and Hank -- 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/CABx2%3DD_3tiYtAEBiNypQZjcZQD3NH1XBJ8C%3DP8D9buYxdZfdqA%40mail.gmail.com.
