channels test hanging issue

[vtjnash]

see e.g https://ci.appveyor.com/project/JuliaLang/julia/builds/23345251/job/9ts99c8wym4toiht

been seeing this for a couple days at least

EDIT: I think this seems likely to be related to #30186 in some way

[vtjnash]

fwiw, I believe the culprit is #30806

[vtjnash]

probably something older, as it also seems to have happened on older builds https://ci.appveyor.com/project/JuliaLang/julia/builds/21512596/job/ym5ol1k2kjg0lg29
https://ci.appveyor.com/project/JuliaLang/julia/builds/21037773/job/opaj4joh6v7406jl
https://ci.appveyor.com/project/JuliaLang/julia/builds/20832326/job/025iqjrfdlueum18

possibly further back than
https://ci.appveyor.com/project/JuliaLang/julia/builds/20355614/job/7sjrnm9asej5to38
even (or that's a different issue, since it's something else that's hung that time)

[vtjnash]

OK, maybe multiple issues here. I downloaded the AV logs, and it's been hanging for a long time:
https://ci.appveyor.com/project/JuliaLang/julia/builds/7261861/job/kob4b2axe33p6uv5 (remember those days, when we could test the whole thing faster than we can run just the Pkg tests today?)

But also most of those I've spot checked passed the channels test, so that might be new.

[vtjnash]

Probably also happened on FreeBSD: https://build.julialang.org/#/builders/29/builds/895