[https://nvbugs/6484986][fix] In UcxConnectionManager::recvConnect, replace the unconditional future.get()…

[trtllm-agent]

Summary

• Root cause: UCX recvConnect() blocks on future.get() without checking the caller-supplied terminate flag, so the sender's response thread is stuck forever when a context-only request times out with no gen peer, deadlocking LLM shutdown at proxy.shutdown()->mpi_future.result().
• Fix: In UcxConnectionManager::recvConnect, replace the unconditional future.get() with a polling loop on ucxx::Request::isCompleted(); on each tick check DataContext.getTransferTerminate() and mIsRunning, and if either signals shutdown, cancel the pending UCX request and return nullptr. The existing recvRequestInfo() already handles nullptr → std::nullopt → clean response loop exit.
• Automated fix generated by repair-bot

Test plan

• Verify fix on the same GPU type as the original failure
• Check for regressions in related tests

Links

• Bug: https://nvbugs/6484986

Dev Engineer Review

• Removed the obsolete waiver for unittest/llmapi/test_llm_pytorch.py::test_llm_context_only_timed_out[None].
• The surrounding waiver entries remain unchanged, with no apparent formatting or scope issues.
• No public API or code changes were introduced.
• No duplicate waiver entry was identified.

QA Engineer Review

• Modified test-list file: tests/integration/test_lists/waives.txt
  • Removed the waiver for test_llm_context_only_timed_out[None].
• No test code, test-db/, or qa/ files were modified.
• Verdict: needs follow-up pending CBTS coverage data.

[coderabbitai]

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Walkthrough

The integration waiver list removes the skip entry for test_llm_context_only_timed_out[None]; surrounding timeout and memory-profiling waivers remain unchanged.

Changes

Integration-test waiver update

Layer / File(s)	Summary
Timeout waiver removal tests/integration/test_lists/waives.txt	Removes the skip entry for unittest/llmapi/test_llm_pytorch.py::test_llm_context_only_timed_out[None] while retaining subsequent waiver entries.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested reviewers: bowenfu, qijune, tburt-nv

🚥 Pre-merge checks | ✅ 2 | ❌ 3

❌ Failed checks (3 warnings)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	The title describes a UCX code fix, but the diff only removes a waiver entry in tests/integration/test_lists/waives.txt.	Rename the title to match the actual change, or update the diff if the code fix is intended.
Description check	⚠️ Warning	The description is informative, but it does not follow the required template sections for Description, Test Coverage, and PR Checklist.	Add the missing template sections and fill in the Description, Test Coverage, and PR Checklist items explicitly.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
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.

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

cpp/tensorrt_llm/executor/cache_transmission/ucx_utils/ucxCacheCommunicator.cpp (1)

621-624: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Name the polling interval.

std::chrono::milliseconds(50) is a newly introduced magic literal. Define a function-local constexpr such as kRecvConnectPollInterval and reuse it.

As per coding guidelines: “Avoid magic literals except 0, nullptr, true, and false; initialize named constants instead, using k-prefixed camelCase names.”

Proposed refactor

+    constexpr std::chrono::milliseconds kRecvConnectPollInterval{50};
     auto const& transferTerminate = ctx.getTransferTerminate();
-    while (future.wait_for(std::chrono::milliseconds(50)) != std::future_status::ready)
+    while (future.wait_for(kRecvConnectPollInterval) != std::future_status::ready)

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@cpp/tensorrt_llm/executor/cache_transmission/ucx_utils/ucxCacheCommunicator.cpp`
around lines 621 - 624, In the wait loop using future.wait_for, replace the
magic 50-millisecond duration with a function-local constexpr named
kRecvConnectPollInterval, then reuse that constant in the polling call while
preserving the existing cancellation behavior.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In
`@cpp/tensorrt_llm/executor/cache_transmission/ucx_utils/ucxCacheCommunicator.cpp`:
- Around line 621-630: Update the shutdown sequence around stopProgressThread()
to set mIsRunning = false before stopping the UCX worker progress thread,
ensuring recvConnect() observes shutdown and can cancel pending requests safely.
In the recvConnect() polling loop, replace the inline 50 ms duration with a
named constant and use it for the future wait timeout.

---

Nitpick comments:
In
`@cpp/tensorrt_llm/executor/cache_transmission/ucx_utils/ucxCacheCommunicator.cpp`:
- Around line 621-624: In the wait loop using future.wait_for, replace the magic
50-millisecond duration with a function-local constexpr named
kRecvConnectPollInterval, then reuse that constant in the polling call while
preserving the existing cancellation behavior.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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📒 Files selected for processing (2)

• cpp/tensorrt_llm/executor/cache_transmission/ucx_utils/ucxCacheCommunicator.cpp
• tests/integration/test_lists/waives.txt

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• tests/integration/test_lists/waives.txt

[chienchunhung]

FYI I created #16688 as the targeted fix for the bug.

[tburt-nv]

Closing based on #16678 (comment)