test(windows): stop the cross-process test starving itself on a loaded runner - #1251
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…d runner The test ran 100 rounds a side, both taking the lock, while a reader thread hammered the same file. Production allows a 2s wait with a 50ms poll, which suits a UI that writes on a click but starves under that much contention: a waiter that loses the race after each poll can exceed the budget, and the acquire then fails by design. That is what turned main red on the merge, not a lost update. 24 rounds a side keeps the property under test and the harness stops being the thing that fails. Measured on this machine, ten runs each way: the test still fails 10 out of 10 with CB_TRAY_XPROC_NOLOCK=1 and passes 10 out of 10 with the lock, so it detects the bug exactly as reliably as before. The production budget and poll are untouched. If sustained contention ever becomes a real workload rather than a test, the poll is the thing to revisit, not the budget.
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mainwent red on the merge of #1248:check (ubuntu-latest)failed withNot a lost update, and not a fault in the lock — the harness starved itself. It ran 100 rounds a side, both sides taking the lock, while a reader thread hammered the same file. Production allows a 2s wait with a 50ms poll, which is right for a UI that writes on a click but not for sustained contention: a waiter that loses the race after each poll can exceed the budget, and the acquire then fails exactly as designed. It passed on the PR branch and failed on main because the runner was busier.
24 rounds a side keeps the property under test. Measured here, ten runs each way:
CB_TRAY_XPROC_NOLOCK=1So it still catches a lost update exactly as reliably as before.
The production budget and poll are deliberately untouched — tuning shipped timings to make a test pass would be the wrong way round. If sustained contention ever becomes a real workload, the 50ms poll is the thing to revisit, since that is what allows starvation, not the 2s budget.