cmd/compile: race detector detects race with close(chan) and len(chan) [1.11 backport]

[randall77]

Considering backporting the fix for #27070 to 1.11.

This was an issue introduced in 1.11. The race detector reported a race between close(chan) and len(chan), where previously (in 1.10) it didn't.

The spec is silent on this issue, so it's technically ok to report a race here, but consensus was that it was worth fixing. But is it worth backporting?
The fix is pretty simple. https://go-review.googlesource.com/c/go/+/135698

[randall77]

@andybons : What's the process for going from CherryPickCandidate to CherryPickApproved?

[andybons]

@randall77 someone on the OSP team reviews and marks whether it should be approved. Since @ianlancetaylor already said as much in #27070 (comment), approving...

[gopherbot]

Change https://golang.org/cl/138179 mentions this issue: [release-branch.go1.11] runtime: ignore races between close and len/cap

[gopherbot]

Closed by merging e535c71 to release-branch.go1.11.