sync::syncs_header_only_forks test is flaky

[altonen]

Is there an existing issue?

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• This is not a support question.

Description of bug

There is a bug somewhere in the code which causes this test to freeze randomly. Bisecting doesn't help beyond a certain point because some of the history doesn't build (e.g., the commit that introduced this test) but this has been an issue since at least commit 66ff3a566e6ee7d85f30fc11d45047bd41854b9e. The code really seems to be stuck as opposed to just polling and waiting for, e.g., a missing block.

Steps to reproduce

I found this most reproducible when running in a virtual terminal and with debug logging enabled for sync target, happens maybe every 5th run.

for i in {1..100}; do RUST_LOG=sync=debug cargo test --release sync::syncs_header_only_forks; done

[ggwpez]

Huh cannot reproduce. Even with taskset -c 0 to just run it on one CPU. Maybe my PC is too fast 😛 ?
Anyway, added it to the ever-growing list of flaky tests paritytech/polkadot-sdk#48 …