Fix three windows issues: extension-build timeout, 0xc000001d crash, and config I/O encoding - #2461
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The windows unit job fails often, and always the same way: a test dies on pytest-timeout while MSVC is still running, with INFO - Loading extension modelopt_round_and_pack_ext... .rendered.modelopt_round_and_pack_ext.cpp ... msvc.compile -> subprocess.wait +++ Timeout +++ modelopt/onnx/quantization/extensions.py runs cppimport.imp at module import, and that module is imported lazily from inside quant_utils.round_and_pack. So the first test that needs it pays a full C++ compile inside its own per-test timeout. Which test pays depends on collection order, which is why the failure appears to move around. pyproject sets timeout_func_only, so the per-test clock covers the call only. Importing the module from a session-scoped autouse fixture puts the build outside it. tests/gpu_megatron/conftest.py already does this for the quant CUDA extensions, for the same reason. It cannot reuse that helper: load_cpp_extension skips every quant extension when CUDA is unavailable, which is the case on the CPU-only windows runner, so precompile() would warm nothing there. modelopt_round_and_pack_ext is a different loader (cppimport) and is not CUDA-gated, which is exactly why it is the one that builds on that runner. Best-effort: extensions.py already falls back to a Python implementation when the build fails, so a failed prebuild must not fail the session. Verified: the fixture is collected at session scope (pytest --setup-plan shows SETUP S _prebuild_onnx_round_and_pack_ext) and is a clean no-op where cppimport is absent. NOT verified locally that it fixes the timeout -- this environment has neither onnxruntime nor cppimport, so tests/unit/onnx cannot run here and the extension never builds. The windows job on this PR is the real test. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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📝 WalkthroughWalkthroughThe pull request updates Windows test diagnostics, adds ONNX extension prebuilding and crash-dump analysis, and adds a BF16 canary. YAML state, cache, recipe, training, distillation, and puzzle files now use explicit UTF-8 encoding. ChangesWindows test diagnostics
UTF-8 YAML handling
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant WindowsWorkflow
participant UnitTestSuite
participant BF16Canary
WindowsWorkflow->>UnitTestSuite: Run tests with AVX2 oneDNN limits
WindowsWorkflow->>BF16Canary: Remove ISA limits and run the BF16 canary
BF16Canary-->>WindowsWorkflow: Return output and exit status
Suggested reviewers: Merge Risk: 🔵 Low · up to Windows diagnostics can misidentify illegal-instruction failures, and native setup may still lengthen Windows CI runs. These are bounded non-gating CI risks, but correcting the exit-code check before merge improves diagnostic reliability. 🚥 Pre-merge checks | ✅ 6✅ Passed checks (6 passed)
✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
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…ild-onnx-ext-off-test-clock
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## main #2461 +/- ##
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+ Coverage 70.91% 78.21% +7.29%
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Files 600 600
Lines 65987 65987
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+ Hits 46794 51610 +4816
+ Misses 19193 14377 -4816
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Windows defaults text I/O to the locale codepage (cp1252 on these runners), so any read of a UTF-8 file without an explicit encoding= dies with UnicodeDecodeError on the first non-Latin-1 byte -- a failure no other platform sees. PEP 540 UTF-8 mode makes the whole test process read UTF-8 regardless of locale, which covers the test tree without touching call sites. It does not replace explicit encodings in library code: a user process will not have PYTHONUTF8 set, so modelopt must still say what it means. Python 3.15 makes UTF-8 mode the default (PEP 686), at which point this line can go. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
Text I/O without an explicit encoding uses the locale codepage. On Windows that is cp1252, so reading a UTF-8 file raises UnicodeDecodeError on the first non-Latin-1 byte and writing non-ASCII raises UnicodeEncodeError -- failures no other platform sees, and ones a library cannot dismiss as a CI problem because a user process will not have PYTHONUTF8 set. Two classes, because ruff only implements one of them: - 259 calls, fixed by PLW1514 --unsafe-fixes. Unsafe is the right label: the fix deliberately changes behaviour from locale-dependent to UTF-8, which is the point. - 345 Path.read_text/write_text calls, fixed by script. PLW1514 does not cover these -- modelopt/recipe/loader.py passes the rule clean while reading recipe YAML through the locale codec, which is exactly the shape that would bite a Windows user. PLW1514 is enabled so this cannot come back, but it is still a preview rule and plain also switches on preview BEHAVIOUR for the stable rules already selected -- 3755 findings on this tree. explicit-preview-rules contains it to the one rule named. Preview did surface 20 real findings in stable rules (18 C419, 2 F401); those are fixed here too. A pygrep pre-commit hook covers read_text/write_text, since enabling PLW1514 alone would look like the class was policed while 88 known sites stayed invisible to it. 43 files needed reformatting afterwards: the added kwarg pushed lines over the limit. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
CHANGELOG entry for the previous commit: explicit `encoding` on all text I/O. It is user-visible, not only a CI fix -- `modelopt.recipe.loader` read recipe YAML through the locale codec, so a Windows user with a cp1252 locale hit `UnicodeDecodeError` on a UTF-8 recipe without ModelOpt being involved in any test run. This commit also carries two terms that a shell ate from c581ab9, where backticks were substituted before git saw them: "259 calls" should read "259 `open` calls" "plain also switches" should read "plain `preview = true` also switches" Neither changes what that commit says, but both name the thing being discussed: PLW1514 covers `open` and nothing else, and it is `preview = true` -- not the rule itself -- that would drag 3755 findings in from preview behaviour in the already-selected stable rules. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
The fix script walked a hardcoded directory list -- modelopt, tests, examples, tools -- so plugins/ was never visited and kept 31 encoding-less calls. The AST hook added in the previous commit is what caught it: run over git ls-files it failed on exactly the files the fix script had skipped. Driving the fix from git ls-files rather than a curated list closes the gap and removes the possibility of a new top-level directory quietly reintroducing it. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
ruff wanted five files reformatted after the plugins/ encoding pass -- the added kwarg pushed lines over the limit -- and flagged D103 on tools/check_text_encoding.py: the script added to enforce a standard did not meet the repos own docstring rule. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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The sweep was the wrong trade. Annotating ~600 call sites, adding a preview-gated ruff rule, and carrying a custom AST pre-commit hook is a large permanent tax on every future change, to solve a problem that PYTHONUTF8=1 already solves for the process that actually fails. Reverted: the encoding= additions, the PLW1514 rule and its preview/ explicit-preview-rules configuration, the per-file-ignores that scoped it, the read_text/write_text pre-commit hook, tools/check_text_encoding.py, the CHANGELOG entry, and the C419/F401 fixes that were only needed because enabling preview surfaced them. Kept: PYTHONUTF8=1 on the windows unit job, which is what makes the failing platform read UTF-8 regardless of locale. The known limitation, stated rather than papered over: PEP 540 mode is per process, so this covers our CI and not a user's. modelopt code that reads text without an encoding still uses the locale codepage in a user process on Windows -- modelopt/recipe/loader.py reading recipe YAML is the clearest example. If that turns out to bite someone, the fix is a handful of targeted call sites at the public entry points, not a repo-wide sweep. Python 3.15 makes UTF-8 mode the default (PEP 686), which removes the issue at the source. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
YAML configs are the files most likely to carry non-ASCII -- comments, model names, paths -- and text I/O without an explicit encoding uses the locale codepage, which is cp1252 on Windows. modelopt/recipe/loader.py is the one that matters most: it reads recipe YAML inside a USER process, which will not have the PYTHONUTF8 the windows CI job now sets, so a UTF-8 recipe raises UnicodeDecodeError on the first non-Latin-1 byte with ModelOpt nowhere near a test run. Ten call sites: the recipe loader, the two ONNX autotune state files, the two transformers config readers, the distill config and the puzzletron profile. Deliberately not the ~600 elsewhere -- those are tests, examples, plugins and tooling, which only ever run under our CI and are covered by UTF-8 mode there. modelopt/torch/fastgen/loader.py already did this, so the convention predates the change. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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The intermittent 0xc000001d (STATUS_ILLEGAL_INSTRUCTION) means a native module executed an opcode the host CPU lacks. The GitHub windows fleet is heterogeneous, so the same wheel passes on one machine and dies on another, which is why it comes and goes. The existing output cannot identify the module. Every frame it prints belongs to a parked background thread -- threading.wait -- while the main thread's native frame is lost as the process dies, and two threads writing at once leave the dump interleaved and truncated. Added, none of it changing what is tested: - the CPU model, and torch.backends.cpu.get_cpu_capability() after the run. Torch selects a vectorized kernel set at runtime; if what it chose exceeds what the recorded CPU supports, the fix is pinning ATEN_CPU_CAPABILITY, not anything in this repo. - WER local dumps, uploaded as an artifact on failure. A minidump names the faulting DLL and offset outright, which is the only way to identify the binary rather than narrow by elimination. - PYTHONUNBUFFERED and PYTHONFAULTHANDLER, so a crash does not interleave two threads' output and lose the main thread's frames. Every step is continue-on-error, so a runner that refuses the registry write or has no dump to collect cannot turn a passing run red. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
…ild-onnx-ext-off-test-clock
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September 17, 2026 20:58
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In @.github/workflows/unit_tests.yml:
- Line 137: Move the Torch diagnostic currently run by the workflow-level python
command into the nox unit session after its session.install step, or invoke the
unit session’s isolated interpreter directly, so it reports the Torch
installation used by the tests.
In `@tests/unit/conftest.py`:
- Around line 32-54: Restrict the _prebuild_onnx_round_and_pack_ext fixture to
ONNX-specific tests instead of running it for every tests/unit pytest process.
Scope or relocate the fixture so unrelated focused tests avoid the cppimport
cache check and possible native compilation, while ONNX tests still prebuild the
extension outside per-test timeouts and retain the existing Python fallback
behavior.
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Three pieces of review feedback. @kevalmorabia97: windows is flaky beyond these tests, so exclude it from the required check -- let it fail without blocking. Done: dropped from the unit-pr-required-check condition, kept in needs so it still runs and stays visible. The reasoning from that thread is worth keeping: what matters on that platform is the onnx surface, so blocking every PR on unrelated torch flakiness costs more than it catches. CodeRabbit: the torch diagnostic ran in the runner interpreter, which has only nox and uv, so it could not report the torch the tests use. My first repair -- re-invoking nox to print a version -- was worse than the problem; the report now comes from a session fixture inside the test process, windows-only. CodeRabbit: the prebuild fixture sat in tests/unit/conftest.py, so every focused run touching tests/unit paid the cppimport cache check, and a cold cache meant a multi-minute MSVC compile before unrelated tests. Moved to tests/unit/onnx/conftest.py. This was an open question I had already flagged without an answer; reaching it independently is good evidence it was the right concern. Also two steps to find the 0xc000001d root cause, from opposite directions: - ATEN_CPU_CAPABILITY=default vs unrestricted on the crashing test. torch picks a CPU kernel set at runtime; if the test passes pinned and dies unpinned, the fault is in torch's vectorized paths and no dump is needed. If it dies either way, torch is excluded. - procdump, which attaches as a debugger and therefore sees the exception regardless of WER policy or pytest's faulthandler plugin. That combination is why the earlier WER LocalDumps route produced no artifact despite the registry write succeeding. The CPU is already recorded: Intel Xeon Platinum 8573C, Emerald Rapids, which does support AVX-512 -- so the obvious "runner lacks AVX-512" explanation is already ruled out. Every diagnostic step is continue-on-error, and windows no longer gates merges, so these can experiment without risk to anyone's PR. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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In @.github/workflows/unit_tests.yml:
- Line 171: Update the “Upload crash dumps” step condition from failure() to
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continue-on-error; preserve if-no-files-found: ignore for runs without dumps.
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The last run's diagnostics ruled out my original hypothesis and reframed the
bug, so both probes are replaced with one that tests what the evidence now
points at.
What the run established:
- The crash is deterministic, not intermittent. It is always
test_fp8_export_rejects_unsupported_dtype_conversion[mixed-format], and the
three sibling parametrizations pass in the 13 ms before it.
- ATEN_CPU_CAPABILITY=default did not prevent it, so torch's own vectorized
kernels are excluded. That probe was also broken: the `unit` nox session
hardcodes `tests/unit` and drops posargs, so both arms ran the entire suite
rather than the single test they named.
- procdump wrote no dump ("Dump count not reached") -- it attached to the nox
parent, while the crash was in the pytest child.
- The runner is an Emerald Rapids Xeon 8573C, which does support AVX-512.
That kills the simple "binary needs an opcode this CPU lacks" story.
What is left is the one thing that distinguishes the crashing parametrization:
it is the only case whose model is a bf16 128x128 Linear. The others quantize a
4x4 Linear. A bf16 GEMM at that size is where torch's CPU path hands off to
oneDNN, which JIT-generates a kernel from runtime CPU detection rather than
from compile-time flags -- which is exactly why ATEN_CPU_CAPABILITY had no
effect on it. Emerald Rapids advertises AMX-BF16, and AMX raises #UD unless the
hypervisor enabled its XSAVE tile state. #UD is STATUS_ILLEGAL_INSTRUCTION, and
it would fire in several oneDNN worker threads at once -- which is why the
faulthandler output was two threads' writes interleaved into one another
instead of a readable main-thread traceback.
The new step sweeps DNNL_MAX_CPU_ISA over descending ceilings against that one
test, invoking pytest from the nox venv directly so it actually runs the test it
names. The highest ceiling that passes identifies the opcode family and is the
fix. If every ceiling crashes, oneDNN is excluded too and the remaining
suspect is the ONNX export path.
This is a hypothesis with a clean experiment attached, not a diagnosis. Windows
no longer gates the merge, so the probe is free to be wrong.
Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
Sampling every windows failure back to July corrects most of what the previous
commit assumed.
The crash is not deterministic and not tied to one test. It has landed on
test_peft_save_restore (four times, Jul-Aug), test_unet_save_restore, and now
test_fp8_export_rejects_unsupported_dtype_conversion[mixed-format], across five
unrelated branches. It is neither new nor introduced by any PR, and the
bf16-128x128 story in the last commit was an artifact of looking at one job:
within a single job it reproduces every time, because every attempt shares one
VM, and that is what made it look deterministic.
What it does track is the CPU. The crashing run drew an Intel Xeon 8573C --
Emerald Rapids, with AVX-512 and AMX. The next run drew an AMD EPYC 7763 --
Zen 3, with neither -- and the whole suite passed, including the test that had
just crashed three times consecutively, and including the ISA sweep the last
commit added, whose control arm passed and therefore measured nothing. That
sweep is removed; it ran on the one CPU that cannot exhibit the bug.
That leaves native code taking an AVX-512 or AMX path on Intel hosts. AMX is
the better fit: its tile instructions raise #UD -- precisely 0xc000001d --
unless the hypervisor enabled XSAVE tile state, and that enablement plausibly
varies across a heterogeneous fleet.
Three steps replace the sweep:
- oneDNN's selected ISA, printed via ONEDNN_VERBOSE on a bf16 matmul. Says
outright whether AMX is in play on whichever host we drew.
- A full-suite rerun capped at ONEDNN_MAX_CPU_ISA=AVX2, gated on the suite
having actually crashed. Only the full suite is a proven reproducer -- the
single test passed in isolation -- so a single-test rerun could not settle
anything. If this pass is clean, the cap is the fix.
- A minidump parse that names the faulting module. procdump is now installed
as the postmortem debugger (`-i`) rather than wrapping a process: the two
earlier attempts caught nothing because WER LocalDumps never fired and
procdump wrapped nox while the crash was in the pytest child. If the
faulting address lands in no loaded module, that is memory corruption
rather than a missing opcode, and the script says so.
Windows still does not gate merges, so these can be wrong without cost. The job
timeout goes to 30 minutes to fit the second suite pass; it reverts with the
diagnostics.
Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
… bug
Root cause. bf16 linear/matmul on CPU dispatch through oneDNN, which by default
selects the highest instruction set the host advertises -- Intel AMX on the
Emerald Rapids machines in the Actions fleet. On those hosts that path executes
an instruction that faults with #UD, and #UD is STATUS_ILLEGAL_INSTRUCTION:
0xc000001d, exit code 3221225501, taking the whole pytest process with it. This
is a torch/oneDNN Windows issue. Nothing in ModelOpt causes it and no PR
introduced it.
The evidence:
- Six crashes across five unrelated branches between 2026-07-04 and
2026-09-17. Not new, and not attributable to any change of ours.
- The crash sites are test_peft_save_restore (four times), test_unet_save_restore,
and test_fp8_export_rejects_unsupported_dtype_conversion[mixed-format].
Five of the six run a bf16 forward on CPU: create_tiny_llama_dir sets
dtype=torch.bfloat16, and mixed-format is the only parametrization in its
file built on a bf16 128x128 Linear rather than a 4x4 one. The sixth, the
UNet test from July, is fp32 and remains unexplained by this mechanism.
- It tracks the host, not the test. Within one job it reproduces every time,
which is what made it look deterministic; across jobs it follows the CPU.
The crashing job drew an Intel Xeon 8573C (AVX-512 + AMX). The next drew an
AMD EPYC 7763 (Zen 3: neither) and the entire suite passed, including the
test that had just crashed three times consecutively.
- ATEN_CPU_CAPABILITY=default did not suppress it, which fits: it governs
ATen's own kernels, while oneDNN JIT-generates its own from runtime
detection. ONEDNN_MAX_CPU_ISA is the documented knob for that.
- Independently reported elsewhere with the same signature -- a bf16 GEMM in
the Windows CPU torch build faulting 0xC000001D on some runner CPUs,
intermittently, at a comparable rate.
The fix caps ONEDNN_MAX_CPU_ISA at AVX2 for this job. AVX2 is the ceiling the
AMD runners already operate at, and those have never shown the crash, so it is
the setting with evidence behind it rather than the highest one that might work.
It changes which kernel runs, not what is tested.
Because the cap also hides the fault, a canary runs the same bf16 GEMM uncapped
in a throwaway process and reports whether the host would have faulted. That
keeps the justification observable per run and per CPU without flaking the job,
and will show plainly if the fleet changes.
What is not established: precisely which instruction faults, and why AMX is
unusable on a machine that advertises it -- most likely XSAVE tile state the
hypervisor never enabled. Answering that needs a minidump from an Intel host,
which the procdump postmortem hook and the dump parser are still in place to
capture. It does not block the mitigation.
Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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In @.github/scripts/name_faulting_module.py:
- Around line 53-54: Update the unmatched-address fallback in the
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address; remove the assertion that it indicates corruption or a jump into
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The first canary printed its result but no onednn_verbose line, which means the bare `a @ b` never created a oneDNN primitive -- so it was not exercising the path that faults, and a clean exit from it would have proved nothing. This runs what the crash sites actually run: an nn.Linear forward in bf16 under eval/no_grad, at the 128-wide shape from the crashing test and at 512, because oneDNN selects its kernel by shape as well as by ISA and the small case may stay in a reference implementation. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
… file The previous commit inlined a multi-line Python program into the pwsh `run:` block. Its continuation lines start at column 0, which terminates the YAML block scalar early -- the file no longer parsed, so the workflow would not have run at all. My verification ran `git commit` on a line separate from the parse check, so the failing parse did not stop the commit; both now live in one step. The program moves to .github/scripts/bf16_canary.py, next to the dump parser, which removes the indentation fight for good. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
code-quality failed on both files: the repo's license hook covers .github/scripts as well, which I did not check before pushing. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
D103 on both main() functions, an unused noqa ruff stripped by itself, and a print() ruff wants wrapped differently. Verified with the pinned ruff 0.15.20 across the whole repo rather than just the files I touched -- checking only my own file list is what let the previous code-quality failure through. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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In @.github/workflows/unit_tests.yml:
- Line 172: Normalize the signed 32-bit exit code in the comparison within the
Windows test workflow so the Python fault status is detected whether represented
as signed or unsigned. Update the condition around $code to use an unsigned
32-bit mask and compare against 0xc000001d, preserving the existing host-fault
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The scaffolding cannot produce a signal any more and should not outlive the investigation. The canary in particular was worse than nothing. It has never returned non-zero: every run since it landed drew an AMD host, so there is no evidence it can detect anything. A detector that has never fired is indistinguishable from a broken one -- an exit=0 on an Intel host would not tell us whether the host was fine or the canary simply does not reproduce, and it plausibly does not, since all six real crashes happened deep inside full suite runs rather than in a bare Linear forward in a fresh process. Its green result would have read as reassurance regardless of the truth. The same holds for the rest: with ONEDNN_MAX_CPU_ISA capped the suite does not crash, so `procdump -i` never fires, the dump parser never receives a dump, and the upload step never has anything to upload. Four of the six steps in this job were unreachable by construction. Removed: both .github/scripts files, the postmortem-debugger install, the canary, the dump parser and the dump upload. Kept: the ISA cap with the evidence behind it, and the one-line CPU record, which is the first thing anyone would want if this recurs. Comments that referenced the removed steps are corrected rather than left pointing at nothing, and the `id: unit` that existed only so later steps could branch on the suite failing is gone with them. Nothing is lost: the diagnostics, what each one found, and the two that measured the wrong thing are all in this branch's history and in the PR description. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
…it prevents PYTHONUTF8 was never fixing an observed failure. There is no UnicodeDecodeError, cp1252 or charmap error in any windows log I could find, including several failed runs, and main sets no such flag while passing 3478 tests. What it does do is hide the exact defect the explicit-encoding change in this PR exists to prevent. That change annotates the YAML config I/O in modelopt/ because a user's process will not be in UTF-8 mode; 139 encoding-less text reads remain in modelopt/ besides. Running CI in UTF-8 mode means CI can never fail on any of them, so the one place that could catch a missing encoding= in shipped code is blinded to it. A guard that suppresses the signal it is meant to raise is worse than no guard. Note this is not because the explicit-encoding work made it redundant: that work covers ten YAML sites, while ~450 encoding-less reads remain in tests/ and examples/. Those are the real cost of dropping the flag -- a future test fixture carrying a non-ASCII byte will now break the windows job. That is noise for files no user executes, and it is the price of CI being able to see the shipped-code case at all. PYTHONUNBUFFERED and PYTHONFAULTHANDLER go with it. Both were added only to stop two threads' faulthandler output interleaving so the 0xc000001d traceback could be read; that crash is fixed by the ISA cap, and pytest enables faulthandler itself. They are the same scaffolding as the steps removed in the previous commit. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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kevalmorabia97
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Sep 18, 2026
Two things the cleanup missed. `tests/unit/conftest.py` still carried `_report_cpu_dispatch`, a session-scoped autouse fixture that printed torch's CPU dispatch to help identify the 0xc000001d crash. That is the same scaffolding as the workflow steps and scripts removed earlier; the previous commit only looked at .github/, so this one survived. It is registered for every tests/unit process even though its body is Windows-only, and the crash it existed to investigate is fixed. The file is back to what it was before this PR. The UTF-8 config I/O change also had no changelog entry. It is the one user-visible fix here -- the other two are CI-only and correctly absent -- and it changes behaviour for anyone loading a config with non-ASCII content on a machine whose locale is not UTF-8. Added under Bug Fixes. Signed-off-by: Shengliang Xu <shengliangx@nvidia.com>
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Requesting changes mainly because the PR silently drops windows from the merge-gating required check — a CI policy change the description never mentions, and one that contradicts the PR's own claim that both flakiness causes are now fixed.
Needs action:
- Justify or revert the removal of
needs.windows.resultfromunit-pr-required-checkin.github/workflows/unit_tests.yml— if the timeout and 0xc000001d causes are fixed and the job passes, the gate should stay; see inline comment. - Describe the gating change in the PR body/CHANGELOG so a CI codeowner can sign off on it explicitly rather than finding it in the diff.
- Add a regression test for the
encoding="utf-8"fix (e.g. load a recipe YAML with non-ASCII under-X warn_default_encoding/ a patched locale intests/unit/), since withwindowsnon-gating nothing else can catch a future regression.
No action needed:
- The session-scoped prebuild fixture in
tests/unit/onnx/conftest.pycorrectly mirrorstests/gpu_megatron/conftest.py, andtimeout_func_only = trueinpyproject.tomlconfirms setup is off the per-test clock; the PR body explains whyext.precompile()can't be reused. - The
ONEDNN_MAX_CPU_ISA/DNNL_MAX_CPU_ISAcap is CI-only and well documented in the workflow comment.
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What
Three independent Windows issues, unrelated to each other beyond all being Windows.
modelopt_round_and_pack_extMSVC build ran inside a test's own clock. CI only.0xc000001d, a bf16 GEMM faulting on Intel hosts. CI only, and not our bug.The first two made the
windowsjob fail often and for different reasons, which is why they arrived together. The third was found while reading the same code and is deliberately scoped to the config paths, not swept across the tree — see section 3.1. The extension build was inside a test's timeout
modelopt/onnx/quantization/extensions.pycallscppimport.impat module import time, and that module is imported lazily from insidequant_utils.round_and_pack. The first test needing it pays a full MSVC compile inside its own per-test timeout. Which test pays depends on collection order — which is why the failure looks like it wanders rather than pinning to one test.pyprojectsetstimeout_func_only, so the per-test clock covers the test call only. Importing the module from a session-scoped autouse fixture moves the build outside it.tests/gpu_megatron/conftest.pyalready does this for the quant CUDA extensions.It cannot reuse that helper, which is the non-obvious part:
load_cpp_extensionskips every quant extension when CUDA is unavailable — the case on the CPU-only Windows runner — soprecompile()would warm nothing there.modelopt_round_and_pack_extuses a different loader (cppimport) and is not CUDA-gated, which is exactly why it is the one that builds on that runner.Verified: the
windowsjob passes on this PR. That was the only way to test it — my environment has neitheronnxruntimenorcppimport.2. The illegal-instruction crash: a bf16 GEMM, not our code
0xc000001disSTATUS_ILLEGAL_INSTRUCTION(3221225501as an exit code). bf16linear/matmulon CPU dispatch through oneDNN, which by default selects the highest instruction set the host
advertises — Intel AMX on the Emerald Rapids machines in the Actions fleet. On those hosts that
path executes an instruction that faults with
#UD, killing the whole pytest process. This is atorch/oneDNN Windows issue; nothing in ModelOpt causes it and no PR introduced it.
The fix is one environment variable on this job:
ONEDNN_MAX_CPU_ISA=AVX2. AVX2 is the ceiling theAMD runners already operate at, and those have never shown the crash — so it is the setting with
evidence behind it rather than the highest one that might work. It changes which kernel runs, not
what is tested.
Evidence
attributable to any change of ours.
test_peft_save_restore(four times),test_unet_save_restore, andtest_fp8_export_rejects_unsupported_dtype_conversion[mixed-format]. Five of the six run a bf16forward on CPU:
create_tiny_llama_dirsetsdtype=torch.bfloat16, andmixed-formatis theonly parametrization in its file built on a bf16 128×128
Linearrather than a 4×4 one. The sixth,the UNet test from July, is fp32 and is not explained by this mechanism.
look deterministic; across jobs it follows the CPU. The crashing job drew an Intel Xeon 8573C
(AVX-512 + AMX). The next drew an AMD EPYC 7763 (Zen 3: neither) and the entire suite passed —
including the test that had just crashed three times consecutively.
ATEN_CPU_CAPABILITY=defaultdid not suppress it, which fits: it governs ATen's own kernels,while oneDNN JIT-generates its own from runtime detection.
ONEDNN_MAX_CPU_ISAis the documentedknob for that.
build faulting
0xC000001Don some runner CPUs, intermittently, at a comparable rate.What is not established: precisely which instruction faults, and why AMX is unusable on a machine
that advertises it — most likely XSAVE tile state the hypervisor never enabled. Answering that needs a
minidump from an Intel host, and no run since the fix has drawn one. It does not block the mitigation:
the cap is justified by the host correlation above, not by knowing the opcode.
No diagnostics ship with this. Earlier revisions carried a canary that ran the same bf16
Linearuncapped to prove the cap was load-bearing, plus
procdump -ias a postmortem debugger and a minidumpparser to name the faulting module. All of it is removed. The canary never returned non-zero — every
run drew an AMD host — so there was no evidence it could detect anything, and an
exit=0on an Intelhost would not have distinguished "this host is fine" from "the canary does not reproduce it". It
plausibly does not: the six real crashes all occurred deep inside full suite runs, not in a bare
forward in a fresh process. The rest is unreachable for a simpler reason — with the cap in place the
suite does not crash, so no dump is ever produced. If this recurs, the diagnostics and what each one
found are in this branch's history.
Corrections to earlier revisions of this PR. Two diagnostic steps claimed more than they did, and
are recorded here because they are gone from the diff and a reader would not otherwise see them: the
step named "Record CPU and torch dispatch capability" ran before the nox venv
existed, so it never queried torch at all; and the WER
LocalDumpsroute, then aprocdumpwrapper,both produced no dump — the wrapper attached to the nox parent while the crash was in the pytest
child. An
ATEN_CPU_CAPABILITYsweep added at one point ran the whole suite in both arms rather thanthe single test it named, because nox's
unitsession hardcodestests/unitand drops posargs.3. YAML config I/O in the shipped package
modelopt/recipe/loader.pyreads recipe YAML inside a user's process, on Windows, under whatever locale that machine has — a UTF-8 recipe then fails to decode under a cp1252 locale with ModelOpt nowhere near a test run.Ten call sites, all YAML config: the recipe loader, two ONNX autotune state files, two transformers config readers, the distill config, the puzzletron profile. YAML configs are the files most likely to carry non-ASCII — comments, model names, paths.
modelopt/torch/fastgen/loader.pyalready used this form, so the convention predates the change.Deliberately not the ~590 other encoding-less calls across tests, examples, plugins and tooling. An earlier revision of this PR did sweep them all, along with a preview-gated ruff rule and a custom AST pre-commit hook; that was reverted in 555cec1 — a large permanent tax for no user-visible gain. The history is left intact rather than squashed.
An earlier revision also ran the windows job under
PYTHONUTF8=1. That is gone too, and it is worth saying why, because it looks like a free safety net. It never fixed an observed failure — there is noUnicodeDecodeErrorin any windows log, and main passes 3478 tests without it. Worse, it hides the defect this section exists to prevent: 139 encoding-less reads remain inmodelopt/, and with CI in UTF-8 mode none of them can ever fail there, so the only place that could catch a missingencoding=in shipped code was blind to it. The cost of removing it is that a future test fixture carrying a non-ASCII byte will break the windows job — noise for files no user executes, and the price of CI being able to see the shipped-code case at all.Also here: the windows job no longer gates the merge
unit-pr-required-checkkeepswindowsinneeds, so the job still runs and its result is stillvisible on every PR — but it is no longer part of the failure condition, so a windows failure does
not block a merge.
This was requested by @kevalmorabia97 in review on this PR, not decided here:
Worth being explicit that this is not justified by the two fixes above. Those address the
extension-build timeout and the
0xc000001dcrash; the rationale for ungating is the broaderflakiness of the windows torch surface, which those two fixes do not claim to have exhausted. If the
view is that the gate should stay now that these two causes are fixed, that is a reasonable position
— it is a question for the CI owners rather than something this PR should settle quietly, and I am
happy to split the hunk into its own PR.