[mhaseeb123]

Description

This PR disables UCX dmabuf (UCX_CUDA_COPY_DMABUF=no, unless already set) in the libcudf_streaming UCXX test environment. Since UCX 1.22, memory type detection exports a dmabuf for every new device buffer, which intermittently segfaults inside cuMemGetHandleForAddressRange on the rapidsmpf progress thread (seen mostly on arm64 CI). The tests don't need dmabuf.

Checklist

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

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[mhaseeb123]

/ok to test e21d857

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[mhaseeb123]

/ok to test c42f774

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• cpp/libcudf_streaming/tests/main/ucxx.cpp

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📝 Summary

Summary by CodeRabbit

• Tests
  • Updated test setup to disable UCX CUDA dmabuf exports by default.
  • Preserves any existing user-provided configuration for this setting.

The UCXX test environment now sets UCX_CUDA_COPY_DMABUF to "no" when it is not already defined. The setting occurs before CUDA and MPI initialization.

Changes: UCX test environment setup

Layer / File(s)	Summary
Set the UCX environment default cpp/libcudf_streaming/tests/main/ucxx.cpp	UCXXEnvironment::SetUp sets UCX_CUDA_COPY_DMABUF to "no" only when the variable is not already defined. The file includes <cstdlib> for environment-variable handling.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to c42f7

No actionable merge-blocking risk remains.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description check		The description explains the UCX dmabuf change, the intermittent segmentation fault, and the affected test environment.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly identifies the main change: mitigating an intermittent segmentation fault in the libcudf_streaming UCX tests.

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[bdice]

This feels like a bug in UCX. We ought to isolate and report it.

I had a different solution in 688c279. What do you think about that? I think I prefer setting env vars in CI scripts rather than test harnesses unless there are benefits I’m overlooking.

[mhaseeb123]

This feels like a bug in UCX. We ought to isolate and report it.

🎯 The env var export here is a workaround, not a fix.

I had a different solution in 688c279. What do you think about that? I think I prefer setting env vars in CI scripts rather than test harnesses unless there are benefits I’m overlooking.

That works. Let me know if I should close this PR (in favor of another) or just adapt your commit in here.

[mhaseeb123]

See: rapidsai/ucxx#784