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torch_c on CPython 3.15t: builds, imports, keeps the GIL (#51 step 1) - #70
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abi3 becomes a default cargo feature; --no-default-features builds a version-pinned _C against a free-threaded interpreter. pyo3 0.29 declares a module GIL-free by default, and the first 3.15t build read sys._is_gil_enabled() == False before any global was audited, so the module now says gil_used = true. tests/api/test_freethreaded.py checks both in a 3.15t subprocess; with the attribute removed it goes red.
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Gate on CI (issue #24)Full gate: 126 suites = 118 run on at least one CI runner + 8 local-only. The local gate (
Local-only: verified by no CI runner (8)
Suites that verified nothing, or failed, on a runner
Every suite, every runner
A SKIP is unverified on that runner, never passed. UNVERIFIED means the suite ran and every one of its tests skipped by name. |
build.py --abi ft builds _C with --no-default-features against a 3.15t target interpreter and tags the wheel from its sysconfig (ftabi.py). Windows, iOS, Android and wasm refuse by name: no free-threaded target CPython, or a Windows path written against python313. publish-pypi gains a build-ft job (host, linux-x86_64, linux-aarch64) on PBS 3.15.0rc1 freethreaded; collect expects those three wheels by name. test_ftwheel 25 ok; GIL-check and tag mutants go red.
Dry run 37287742911 built both Linux cp315t wheels and then refused them: verify() remapped `expected` for ft but still searched the archive for the target's abi3 member. The host passed only because its target is None. test_verify_finds_the_ft_member_for_a_cross_target was red on the old code.
4 tasks
…am's are (#76) Both were process-wide: torch.no_grad() in one thread stopped grad_fn recording in another, and torch.device('meta') on one thread moved another thread's factories to meta. Wrong with the GIL on, not only on 3.15t. tensor.rs GRAD_ENABLED is a thread_local Cell; the bootstrap's grad flag and _MODE_STACK sit on threading.local. tests/api/test_threadstate.py: 3 tests, green on upstream torch, red on the shim before, green after.
… out from under a live draw (#76) Streams were Box::leak'ed and reclaimed by Box::from_raw in stream_free, sound only while a kernel's guard and the generator's __del__ could not overlap under the GIL. stream() now returns a GenGuard that holds its own Arc clone; stream_free drops the table's reference. The new cargo test frees a locked stream and reuses its memory: SIGSEGV on the old code, green now.
…; test_threadstate sets TORCH_USE_RTLD_GLOBAL CAPTURING was cleared by whichever thread ended its capture first, so a thread still mid-capture stopped recording and its later ops vanished from its trace. It is now an AtomicUsize of open regions (one per thread at most, since capture_begin refuses nesting); the door still pays one relaxed load. test_threadstate.py never ran in the gate before this commit: it died at import torch for want of TORCH_USE_RTLD_GLOBAL, which every other suite that imports torch sets. Now 4 ok in the gate (2010 -> 2014).
… mode (#51, #76) 8 threads behind a Barrier in a 3.15t subprocess that overrides gil_used. Against a build without #76's fixes, grad and mode go red ('another thread's no_grad applied here', 'pop from an empty torch function mode stack'); with them all three are green. The RNG case stays green on the old code too: the use-after-free is proven by the cargo test, not by this hammer. The first version collected errors under the wrapper's name and so could never fail; the nullification above is how that was found. Also git-ignores target-ft/, build.py --abi ft's default cargo dir.
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This branch now also contains #77 (merged in locally so the 3.15t hammer could exercise its fixes), plus the hammer in
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CI evidence (run 37321276340, d1f265e):
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Paused (user's instruction). The macOS job was re-run on run 37321276340 after an ENOTFOUND artifact upload. Remaining #51 steps: the 9 'unclear' audit items, the full gate on 3.15t (blocked: no upstream torch build for 3.15t to compare against), and Py_mod_gil. |
PBS release 20261013 ships 3.15.0 freethreaded for aarch64-apple-darwin and both linux-gnu triples. The ft rows now fetch from their own PBS_FT_RELEASE so the cp313-abi3 interpreter pin (PBS_RELEASE 20260825, 3.13.15) stays where the published 0.1.0b5 wheels were built. test_ftwheel now requires 3.15.0 final and no 3.15 pre-release anywhere; it was red on the rc1 pin. Locally: _C built against PBS 3.15.0t, tests/api/test_freethreaded.py 5/5 ok (including the PYTHON_GIL=0 hammer).
This was referenced Oct 16, 2026
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Refs #51 (step 1 of the order set on the issue; the issue stays open).
Feature added
torch_cbuilds against CPython 3.15.0rc1+freethreaded:cargo build --release --no-default-featureswithPYO3_PYTHONset to the 3.15t interpreter.abi3is now a default cargo feature, so the cp313-abi3 build is unchanged (cargo check --releasepasses).torch.ones(2)+1gives[2., 2.]and_aten_implementedis present. Grade: reaches.Defect fixed
sys._is_gil_enabled() == Falsebefore any global had been audited.#[pymodule(gil_used = true)]keeps the GIL until the audit and its thread tests land. 3.15t now re-enables the GIL and warns.Test added
tests/api/test_freethreaded.py(2 tests,BOTHin the manifest). It skips by name unlessTORCHNATIVE_FT_PYTHONandTORCHNATIVE_FT_STAGEare set. Run live on the host: 2 ok.gil_used = true, andtest_module_keeps_the_gil_until_the_audit_landswent FAIL.Not done (remaining #51 criteria)
publish-pypi.ymlfor the macOS, iOS, Android, Linux and Windows targets.Py_mod_gil.