runtime: TestSelectFairness failures with "unfair select"

[bcmills]

#!watchflakes
post <- pkg == "runtime" && test == "TestSelectFairness"

greplogs --dashboard -md -l -e 'FAIL: TestSelectFairness .*(?:\n .*)*unfair select'

2022-04-20T16:05:16-338a817/illumos-amd64
2022-03-23T19:31:43-2792a41/netbsd-386-9_0
2020-08-19T00:10:22-98a0071/js-wasm

@golang/runtime: the comment for this test suggests that it has a confidence level of “six nines”, which would be one spurious failure per ~1M runs. Is it still in line with that target?

See previously #34808, #22047.

[mengzhuo]

The "six nines" requires less than 244 out of 10000 trials however the fail logs shows 5245,5253,5246.

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
post <- pkg == "runtime" && test == "TestSelectFairness"

2022-11-18 17:59 linux-386-buster go@b2faff18 runtime.TestSelectFairness (log)

--- FAIL: TestSelectFairness (0.01s)
    chan_test.go:488: 5256 4744 0.5256 0.025599999999999956
    chan_test.go:490: unfair select: in 10000 trials, results were 5256, 4744

— watchflakes