[adenzhou1350]

Status

Closed as superseded by #20446, merged as 39f300f1bd910bdad8f93c2b8f65e47cbaf6028c on October 27.

Upstream now shares CPU storage by filename directly, without switching PyTorch's process-wide sharing strategy. The original try/finally and lock patch is no longer needed.

Verification of the upstream replacement

October 28, Linux / Python 3.12.3 / Torch 2.13.0+cu130, CPU operations only:

• Exact source before the replacement (0a03c3ed057f): injected filename-storage failure leaks file_descriptor to file_system.
• Exact current-main source (581b83208): the same exception propagates with file_descriptor unchanged before, during and after serialization.
• Nine real CPU dump/rebuild round trips pass, including eight across two concurrent workers.

This is standalone raw-module validation with genuine Torch, not the full TensorRT package, official L0 suite or CUDA validation. No new code was pushed; the original fork head remains 4041586a1849e36bfa70da88db1284fdf6c6824e.

AI assistance was used for the original implementation and this maintenance verification.

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Walkthrough

CPU tensor serialization now serializes sharing-strategy changes across threads. It restores the original strategy after storage reduction. A concurrency test verifies that overlapping CPU serialization calls do not enter the strategy window together.

Changes

Sharing strategy synchronization

Layer / File(s)	Summary
Serialization sharing-strategy guard tensorrt_llm/_torch/shared_tensor/shared_tensor.py, tests/unittest/_torch/misc/test_share_tensor.py	dump_to_dict uses a module-level lock while it selects file_system, reduces CPU storage, and restores the prior strategy in finally. The test verifies that concurrent calls serialize access and restore file_descriptor.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 40415

The change restores the prior tensor-sharing strategy after CPU serialization failures, with no actionable merge-blocking risk identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 62.50% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 8 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 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.
Title check	✅ Passed	The title uses the required [None][fix] format and clearly describes the primary change: restoring the tensor sharing strategy after errors.
Description check	✅ Passed	The description explains the issue, solution, regression tests, validation checks, and checklist status. It identifies the failure recovery and concurrency coverage and states that no API or other rep…

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[brnguyen2]

Approving — the comments below are optional touch-ups, not blockers.

The try/finally is the right fix for the leak and the test pins it (the file lives under unittest/_torch/misc, which l0_h100.yml and l0_b200.yml already collect as a directory, so it will run in CI).

Two things to clean up:

• The PR description embeds a "Dev Engineer Review"/"QA Engineer Review" block asserting that the diff contains only import-formatting changes and that the regression test is absent. That's wrong — the finally and test_share_cpu_tensor_restores_strategy_on_error are both in the diff. Please delete that block so reviewers and git log aren't left with a contradicting summary.
• The rewrapped comment at [tensorrt_llm/_torch/shared_tensor/shared_tensor.py:456](https://github.com/NVIDIA/TensorRT-LLM/pull/19503/files#diff-31c8f32a9be5d5b5068757beaad6e7b7ed78775af24029247840bb1a4ce0d916R456) is an unrelated reflow. Harmless, but it makes the diff look bigger than the fix.

[zhaoyangwang-nvidia]

Approve with nits. Separately: the auto-generated "Dev Engineer Review" / "QA Engineer Review" sections at the bottom of the description claim the diff is import-formatting only and that the regression test is missing, which contradicts the actual diff — could you drop them so the description doesn't mislead anyone reading this later?

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Actionable comments posted: 1

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Inline comments:
In `@tensorrt_llm/_torch/shared_tensor/shared_tensor.py`:
- Line 460: Add a regression test in the shared-tensor test suite for concurrent
CPU serialization: mock reduce_storage(), block the first invocation with a
threading.Event, start a second CPU dump_to_dict() call, and assert the second
reducer cannot begin until the first invocation releases the event, validating
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[adenzhou1350]

Thanks @brnguyen2 and @zhaoyangwang-nvidia for the reviews. The contradictory generated Dev Engineer Review / QA Engineer Review sections are gone; the description now covers the actual try/finally restoration, strategy lock, and failure/concurrency regressions. The inline review threads are resolved.

Could a maintainer trigger the required blossom/L0 CI for this approved PR? It currently shows 15 workflows awaiting approval and blossom-ci Expected. For the related pending handoffs, #19500 now has a successful L0 #62804 run on e88683b, while the requested main-branch Mooncake fix #19813 still awaits CI/review. Please let me know which remaining checks or changes are needed for these to proceed.

[JunyiXu-nv]

Runtime part (shared_tensor.py) LGTM: the sharing strategy is now restored in finally and the swap is serialized.

[github-actions]

Automatically added "ci: full pre-merge approved" because this PR has satisfied the required GitHub review approvals. Unresolved review conversations and other required checks remain independent merge requirements.

[adenzhou1350]

Closing as superseded by #20446, merged in 39f300f1bd910bdad8f93c2b8f65e47cbaf6028c. That change uses filename storage sharing directly and no longer changes PyTorch's process-wide sharing strategy, removing the failure/concurrency window this PR guarded.

I verified exact raw source with genuine Torch 2.13 CPU on Linux/Python 3.12: at parent 0a03c3ed057f, an injected filename-storage error leaves file_descriptor changed to file_system; on current main 581b83208, the same error propagates while the strategy remains file_descriptor throughout. Nine real CPU dump/rebuild round trips, including eight across two concurrent workers, also pass on main. This was a standalone source-module probe, not the full TensorRT package, official L0 suite or CUDA validation.

The original fork implementation is unchanged. Resolving the conflict by keeping its temporary global switch would restore work that upstream has removed, so this PR is no longer needed. Thanks for reviewing it.