Relax racy fairness test

[jonhoo]

Fixes #477

[ghost]

This looks good to me, but seems like CI is broken. I'm inclined to merge anyway and take care of that later...

[taiki-e]

seems like CI is broken

It seems due to signal-hook's MSRV was increased to 1.31: vorner/signal-hook@e63edcf

[taiki-e]

It seems due to signal-hook's MSRV was increased to 1.31: vorner/signal-hook@e63edcf

So we need to either:

• Downgrade signal-hook's patch version in MSRV CI (add cargo update -p signal-hook --precise 0.1.13):
  

  crossbeam/.github/workflows/ci.yml

  Lines 40 to 44 in 485971e

  	- name: Downgrade dependencies
  	if: matrix.rust == '1.28.0'
  	run: |
  	cargo generate-lockfile
  	cargo update -p cfg-if --precise 0.1.9

• Bump crossbeam's MSRV to 1.31

[jonhoo]

One upside of the latter is that it would also mean #487 no longer needs to bump the MSRV. But that's definitely minor.

[taiki-e]

I have tried the first way (downgrade deps) locally, but it seems that the MSRV of so many dependencies is actually increasing, so this seems to be difficult...

[jonhoo]

One issue here is that the docs say:

The minimum supported Rust version is 1.28. Any change to this is considered a breaking change.

That is a very strict policy. The policy should (probably) instead be "six months" or something? But as it stands, we'd need to issue new major releases of all the crossbeam crates to do that... It also definitely gets weird since people will have to run through all sorts of hoops to actually get it running with 1.28 — so are we even really supporting MSRV 1.28?

[taiki-e]

I agree with the current policy needs to be changed as suggested in #444 (comment).

It also definitely gets weird since people will have to run through all sorts of hoops to actually get it running with 1.28 — so are we even really supporting MSRV 1.28?

I mentioned this in #428 (comment), but I think it is ok to set MSRV based on the compilable version (without downgrading the dependencies).

[ghost]

Let's merge and fix CI in a follow-up PR.