Multi-threading deadlock on Windows

[vlandau]

Need to identify cause. It is only exposed on Windows in Travis and Appveyor with Julia 1.3, doesn't happen in Julia 1.2. @ranjanan or @ViralBShah any advice would be greatly appreciated!

Here's a post on the Julia discourse I made with links to relevant code blocks in Omniscape.jl

[ViralBShah]

We've received similar reports on windows. Is this reliably failing?

@JeffBezanson @vtjnash

[vlandau]

@ViralBShah Yes, it consistently fails, but only on Travis and Appveyor (maybe due to the more limited hardware resources of those VMs?)

[ViralBShah]

Do you have a windows desktop/laptop to try on?

[vlandau]

It has been tested on two different windows machines locally and passed on both. I also tested it with JULIA_NUM_THREADS set to 1 on one of the machines (which is what the Travis and Appveyor VMs have) and it passed.

[vlandau]

I do have access to a Windows machine to do additional local testing if/as needed.

[ViralBShah]

It is possible that the Travis VMs are constrained. We will need a way to reproduce this reliably on a local setup in order to debug.

[vlandau]

There may be a way to set up a Docker image with limited access to resources (?). I'll look into this a bit.

[vlandau]

Looks like windows in Travis CI uses Window server 2016. Some more info: https://docs.travis-ci.com/user/reference/overview/#what-infrastructure-is-my-environment-running-on

Also, https://docs.docker.com/config/containers/resource_constraints/

Can't get into this until after Jan 2nd.

[vlandau]

@ViralBShah do you think it's worth trying to debug from within an Appveyor VM?

There is a way to get inside the VM via remote desktop.
https://www.appveyor.com/docs/how-to/rdp-to-build-worker/

[ViralBShah]

I think it might be this one: JuliaLang/julia#34225

We should wait for it.

[ViralBShah]

Until 1.3.2 (assuming that's where the fix will be), it may be best to stay with Julia 1.2.