Warn when ManagedMemoryResource is created without concurrent managed access#1618
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Andy-Jost merged 1 commit intoNVIDIA:mainfrom Feb 17, 2026
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/ok to test f7eeec8 |
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kkraus14
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Feb 13, 2026
| "allocation is forbidden while any GPU kernel is in flight, even " | ||
| "if the kernel does not touch that allocation. Failing to " | ||
| "synchronize before host access will cause a segfault. " | ||
| "See: https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#um-coherency-hd", |
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I think we want https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#gpu-exclusive-access-to-managed-memory as the link?
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Sure, that's a bit more specific
… access Platforms where Device.properties.concurrent_managed_access is False silently allow managed memory allocation but segfault on unsynchronized host access. Emit a one-time UserWarning at construction time so users get actionable guidance before hitting a crash. Also skip test_build_hooks.py when setuptools is unavailable (Python 3.14+). Closes NVIDIA#1607 Co-authored-by: Cursor <cursoragent@cursor.com>
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/ok to test d8c876f |
leofang
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Summary
UserWarningwhenManagedMemoryResourceis created on a platform whereDevice.properties.concurrent_managed_accessis False. On such platforms, unsynchronized host access to managed memory causes a segfault.test_build_hooks.pywhensetuptoolsis unavailable (Python 3.14+).Closes #1607
Changes
cuda/core/_memory/_managed_memory_resource.pyx: Add_check_concurrent_managed_accesshelper with double-checked locking (warn-once pattern), andreset_concurrent_access_warning()for testing.tests/test_managed_memory_warning.py: New test file verifying the warning fires and only fires once.tests/test_build_hooks.py: Addpytest.importorskip("setuptools").Test Coverage
test_warning_emitted: Verifies the warning content (category, message text).test_warning_emitted_only_once: Verifies warn-once behavior across multiple resource creations.concurrent_managed_access=False).Made with Cursor