coverage: expand resource, cache, and DLPack regression coverage

[rluo8]

Description

Expand cuda.core regression coverage with 35 new tests and additional cases in existing tests.

• Extend graph-node reconstruction coverage for device memcpy, managed allocations, and peer-access metadata; validate invalid adjacency removal and kernel-node updates.
• Cover managed-buffer validation, closed-buffer guards, VMM input validation, and stream workqueue resource metadata.
• Exercise program-cache key generation, optional compiler discovery, disappearing cache entries, and file-permission handling.
• Add DLPack coverage for CUDA-host/managed stream handling, dtype-width validation, missing ml_dtypes, and C exchange API exception propagation.
• Cover NVVM compilation with a log sink, the NVRTC bundled-header version boundary, system-event validation, and kernel/array object behavior.

Changes are limited to tests and test comments.

Validation

• All added tests passed on supported local test systems with Blackwell, Hopper, and Ampere GPUs.
• Capability-dependent tests were skipped where unsupported.
• All pre-commit checks passed.

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📥 Commits

Reviewing files that changed from the base of the PR and between a94c136 and 2fe1140.

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📒 Files selected for processing (7)

• cuda_core/tests/graph/test_graph_definition_lifetime.py
• cuda_core/tests/memory/test_managed_ops.py
• cuda_core/tests/test_green_context.py
• cuda_core/tests/test_module.py
• cuda_core/tests/test_program.py
• cuda_core/tests/test_tensor_map.py
• cuda_core/tests/test_utils_dlpack.py

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📝 Summary

Summary by CodeRabbit

• Tests
  • Expanded coverage for CUDA graph reconstruction and node lifetimes, managed memory, context resources, system events, and input validation.
  • Added checks for program compilation and caching, kernel behavior, tensor maps, opaque arrays, and DLPack interoperability.
  • Verified error handling and object behavior across additional edge cases, including closed buffers, invalid arguments, and cache failures.

Walkthrough

This PR expands cuda_core tests across graph behavior, memory and resource APIs, program compilation and caching, kernel and array APIs, and DLPack validation. It adds checks for invalid inputs, closed objects, version gates, and filesystem race conditions.

Changes

Graph API Tests

Layer / File(s)	Summary
Graph node reconstruction cuda_core/tests/graph/test_graph_definition_lifetime.py	Reconstruction cases cover host and device memcpy nodes and allocation nodes with peer access or managed memory. Tests apply capability and build-version gates.
Graph mutation and kernel-node lifecycle cuda_core/tests/graph/test_graph_definition_mutation.py, cuda_core/tests/graph/test_graph_node_update.py	Tests check invalid adjacency removal, operations after source-node destruction, and updates to cooperative definition nodes.

Memory API Tests

Layer / File(s)	Summary
Managed-buffer attributes cuda_core/tests/memory/test_managed_ops.py	Tests check invalid values for the accessed-by set and attribute queries after buffer closure. Fixture comments describe coverage across both buffer sources.
Allocation argument validation cuda_core/tests/test_memory.py	A test checks that modify_allocation rejects a non-Buffer argument with TypeError.

CUDA Context and Resource Tests

Layer / File(s)	Summary
SM discovery and workqueue resources cuda_core/tests/test_green_context.py	Tests compare preferred co-scheduled SM discovery with native driver results and check primary-context stream workqueue properties against the device resource.

System Event Tests

Layer / File(s)	Summary
Event argument validation cuda_core/tests/system/test_system_events.py	Tests check the exceptions raised for an invalid event type and a non-container argument.

Program Compilation and Cache Tests

Layer / File(s)	Summary
Compilation and version-boundary behavior cuda_core/tests/test_program.py	Tests check NVVM compilation with a log sink and the NVRTC 13.2/13.3 bundled-headers boundary.
Program cache-key inputs cuda_core/tests/test_program_cache.py	Tests cover NVVM source normalization and fingerprint failures, PTX linker-selection failures, and cold nvJitLink imports.
File cache race and error paths cuda_core/tests/test_program_cache.py	Tests cover cache operations under filesystem errors and concurrent file disappearance, including size accounting and eviction.

Kernel Object Tests

Layer / File(s)	Summary
Kernel identity and representation cuda_core/tests/test_module.py	Tests compare kernels by handle, check hashing and inequality, and verify the representation prefix.

Tensor Map and Opaque Array Tests

Layer / File(s)	Summary
Tensor-map and opaque-array validation cuda_core/tests/test_tensor_map.py, cuda_core/tests/test_texture_surface.py	The tensor-map host-view test supplies an explicit interleave value. Opaque-array tests check format rejection, representation fields, and copy argument types.

DLPack Tests

Layer / File(s)	Summary
Capsule, dtype, and shape validation cuda_core/tests/test_utils_dlpack.py	Tests cover CUDA-host and CUDA-managed producer capsules, missing ml_dtypes behavior, and dtype lane-width shape validation.
C export error propagation cuda_core/tests/test_utils_dlpack.py	Tests check BufferError propagation from managed-tensor and borrowed-DLTensor export entry points.

Suggested reviewers: seberg

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Priority: ⬇️ Low

Change: Other

Merge Risk: 🟡 Moderate · up to 2fe11

A VMM-capable test run may fail because its expected error text does not match the implementation. Resolve that mismatch before merging; the texture-surface assertions may also need less wording-sensitive checks.

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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Actionable comments posted: 2

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: Repository: NVIDIA/cuda-python/.coderabbit.yaml
• Review profile: CHILL
• Plan: Enterprise
• Run ID: 0978b463-1b3d-4ef9-bdec-31e3dbe79d35

📥 Commits

Reviewing files that changed from the base of the PR and between a2b1e31 and a94c136.

📒 Files selected for processing (13)

• cuda_core/tests/graph/test_graph_definition_lifetime.py
• cuda_core/tests/graph/test_graph_definition_mutation.py
• cuda_core/tests/graph/test_graph_node_update.py
• cuda_core/tests/memory/test_managed_ops.py
• cuda_core/tests/system/test_system_events.py
• cuda_core/tests/test_green_context.py
• cuda_core/tests/test_memory.py
• cuda_core/tests/test_module.py
• cuda_core/tests/test_program.py
• cuda_core/tests/test_program_cache.py
• cuda_core/tests/test_tensor_map.py
• cuda_core/tests/test_texture_surface.py
• cuda_core/tests/test_utils_dlpack.py

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