Fix flaky StreamPoolTest.ConcurrentThreadsGetDistinctStreams

[vuule]

Description

ConcurrentThreadsGetDistinctStreams relied on a latch to keep its two threads overlapping, but the latch only guarantees that both threads have started, not that both have acquired a stream pool.

Each thread now takes its pool before waiting on the latch, so both pools are live at the same time.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[vuule]

/ok to test f686451

[mythrocks]

Nice one.

[mythrocks]

This can't have an effect on the spark-rapids-jni CI pipeline. The error there is because cudf-spark-jni needs to account for rapidsai/rmm#2527. I'm working on fixing that.

Please ignore that failure.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 8f09dc1 and f686451.

📒 Files selected for processing (1)

• cpp/tests/utilities_tests/stream_pool_tests.cpp

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📝 Walkthrough

Summary by CodeRabbit

• Tests
  • Improved concurrency test coverage to verify simultaneous stream-pool acquisition across threads.
  • Added clearer comments describing stream-pool creation and reuse after thread termination.

Walkthrough

The concurrency test now acquires and records each thread’s initial streams before the latch. Comments describe first-use pool creation and retired-pool adoption after thread exit.

Changes

Stream-pool concurrency test

Layer / File(s)	Summary
Pre-latch stream acquisition cpp/tests/utilities_tests/stream_pool_tests.cpp	Each thread requests and records its initial streams before waiting on the latch. Comments document pool creation and retired-pool adoption.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to f6864

This is a localized test synchronization fix with no actionable merge-blocking risk remaining after normal checks and review.

Suggested reviewers: vyasr, mythrocks

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the flaky test and states that the pull request fixes it. It matches the main change.
Description check	✅ Passed	The description accurately explains the latch race and the change that ensures both threads acquire pools before proceeding.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[vuule]

/merge