code review 11549043: spec: clarify a couple of issues about channels

spec: clarify a couple of issues about channels

1. They are FIFOs.
2. They are safe for concurrent access.

Fixes issue 5911.

[r, 2013-07-18 22:16:35]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go/

[dvyukov, 2013-07-19 12:09:14]

https://codereview.appspot.com/11549043/diff/1/doc/go_spec.html
File doc/go_spec.html (right):

https://codereview.appspot.com/11549043/diff/1/doc/go_spec.html#newcode4130
doc/go_spec.html:4130: Channels act as first-in-first-out queues: if a single
goroutine sends on a channel values
Why is this in the "Send statements" section? I would expect it to be in
"Channel types".

https://codereview.appspot.com/11549043/diff/1/doc/go_spec.html#newcode4135
doc/go_spec.html:4135: A single channel may be used for send and receive
this should also include close/cap/len

[r, 2013-07-22 11:44:43]

https://codereview.appspot.com/11549043/diff/1/doc/go_spec.html
File doc/go_spec.html (right):

https://codereview.appspot.com/11549043/diff/1/doc/go_spec.html#newcode4130
doc/go_spec.html:4130: Channels act as first-in-first-out queues: if a single
goroutine sends on a channel values
On 2013/07/19 12:09:14, dvyukov wrote:
> Why is this in the "Send statements" section? I would expect it to be in
> "Channel types".

It's not a property of the types, it's a property of operations on the types. A
somewhat artificial distinction I admit but I started by trying to put the text
there and it just didn't feel right, so I put it here.

https://codereview.appspot.com/11549043/diff/1/doc/go_spec.html#newcode4135
doc/go_spec.html:4135: A single channel may be used for send and receive
On 2013/07/19 12:09:14, dvyukov wrote:
> this should also include close/cap/len

Done.

[r, 2013-07-22 11:45:33]

Hello golang-dev@googlegroups.com, dvyukov@google.com (cc:
golang-dev@googlegroups.com),

Please take another look.

[dvyukov, 2013-07-23 08:50:37]

LGTM

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html
File doc/go_spec.html (right):

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html#newcode4131
doc/go_spec.html:4131: that are received by a single goroutine, the values are
received in the order sent.
Just want to make sure that the "if a single goroutine sends..." part is meant
only as an example of FIFO. Because it's possible to observe and rely on FIFO in
scenarios with multiple senders and receivers as well. Readers must understand
that FIFO guarantees are not limited to "single sender goroutine" case.

[r, 2013-07-25 06:23:09]

That's what I mean and what I believe it says. Anyone else?

[adg, 2013-07-25 06:29:40]

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html
File doc/go_spec.html (right):

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html#newcode4130
doc/go_spec.html:4130: Channels act as first-in-first-out queues: if a single
goroutine sends on a channel values
I would split.

...queues. For example, if a single...

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html#newcode4139
doc/go_spec.html:4139: by any number of goroutines without further
synchronization.
how about

"by concurrently executing goroutines" ?

[r, 2013-07-25 12:04:56]

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html
File doc/go_spec.html (right):

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html#newcode4130
doc/go_spec.html:4130: Channels act as first-in-first-out queues: if a single
goroutine sends on a channel values
On 2013/07/25 06:29:40, adg wrote:
> I would split.
> 
> ...queues. For example, if a single...

Done.

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html#newcode4131
doc/go_spec.html:4131: that are received by a single goroutine, the values are
received in the order sent.
On 2013/07/23 08:50:37, dvyukov wrote:
> Just want to make sure that the "if a single goroutine sends..." part is meant
> only as an example of FIFO. Because it's possible to observe and rely on FIFO
in
> scenarios with multiple senders and receivers as well. Readers must understand
> that FIFO guarantees are not limited to "single sender goroutine" case.

Done.

https://codereview.appspot.com/11549043/diff/7001/doc/go_spec.html#newcode4139
doc/go_spec.html:4139: by any number of goroutines without further
synchronization.
On 2013/07/25 06:29:40, adg wrote:
> how about
> 
> "by concurrently executing goroutines" ?

that's redundant.

[r, 2013-07-25 12:05:16]

Hello golang-dev@googlegroups.com, dvyukov@google.com, adg@golang.org (cc:
golang-dev@googlegroups.com),

Please take another look.

[r, 2013-07-31 21:12:43]

*** Submitted as https://code.google.com/p/go/source/detail?r=43f967f62292 ***

spec: clarify a couple of issues about channels

1. They are FIFOs.
2. They are safe for concurrent access.

Fixes issue 5911.

R=golang-dev, dvyukov, adg
CC=golang-dev
https://codereview.appspot.com/11549043