--disable-gil --enable-experimental-jit=yes-off: test_jit_is_active fails

Bug report

Bug description:

Hello.

When we started to build the JIT in Fedora's Python, we didn't do it for the freethreading build, as I was told it's not yet ready. I circled back to the referenced issue https://github.com/python/cpython/issues/118844 and saw it is long closed. Hence, I tried to build the JIT with the freethreading build as well. It builds fine, but the tests fail:

Re-running test_sys in verbose mode (matching: test_jit_is_active)
test_jit_is_active (test.test_sys.TestSysJIT.test_jit_is_active) ... FAIL
======================================================================
FAIL: test_jit_is_active (test.test_sys.TestSysJIT.test_jit_is_active)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builddir/build/BUILD/python3.15-3.15.0_a2-build/Python-3.15.0a2/Lib/test/test_sys.py", line 2275, in test_jit_is_active
    assert_python_ok("-c", script.format(enabled=available), PYTHON_JIT="1")
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/python3.15-3.15.0_a2-build/Python-3.15.0a2/Lib/test/support/script_helper.py", line 182, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/builddir/build/BUILD/python3.15-3.15.0_a2-build/Python-3.15.0a2/Lib/test/support/script_helper.py", line 167, in _assert_python
    res.fail(cmd_line)
    ~~~~~~~~^^^^^^^^^^
  File "/builddir/build/BUILD/python3.15-3.15.0_a2-build/Python-3.15.0a2/Lib/test/support/script_helper.py", line 80, in fail
    raise AssertionError(f"Process return code is {exitcode}\n"
    ...<10 lines>...
                         f"---")
AssertionError: Process return code is 1
command line: ['/builddir/build/BUILD/python3.15-3.15.0_a2-build/Python-3.15.0a2/build/freethreading-debug/python', '-X', 'faulthandler', '-c', '\nimport _testcapi\nimport _testinternalcapi\nimport sys\n\ndef frame_0_interpreter() -> None:\n    assert sys._jit.is_active() is False\n\ndef frame_1_interpreter() -> None:\n    assert sys._jit.is_active() is False\n    frame_0_interpreter()\n    assert sys._jit.is_active() is False\n\ndef frame_2_jit(expected: bool) -> None:\n    # Inlined into the last loop of frame_3_jit:\n    assert sys._jit.is_active() is expected\n    # Insert C frame:\n    _testcapi.pyobject_vectorcall(frame_1_interpreter, None, None)\n    assert sys._jit.is_active() is expected\n\ndef frame_3_jit() -> None:\n    # JITs just before the last loop:\n    # 1 extra iteration for tracing.\n    for i in range(_testinternalcapi.TIER2_THRESHOLD + 2):\n        # Careful, doing this in the reverse order breaks tracing:\n        expected = True and i >= _testinternalcapi.TIER2_THRESHOLD + 1\n        assert sys._jit.is_active() is expected\n        frame_2_jit(expected)\n        assert sys._jit.is_active() is expected\n\ndef frame_4_interpreter() -> None:\n    assert sys._jit.is_active() is False\n    frame_3_jit()\n    assert sys._jit.is_active() is False\n\nassert sys._jit.is_active() is False\nframe_4_interpreter()\nassert sys._jit.is_active() is False\n']
stdout:
---
---
stderr:
---
Traceback (most recent call last):
  File "<string>", line 37, in <module>
    frame_4_interpreter()
    ~~~~~~~~~~~~~~~~~~~^^
  File "<string>", line 33, in frame_4_interpreter
    frame_3_jit()
    ~~~~~~~~~~~^^
  File "<string>", line 27, in frame_3_jit
    assert sys._jit.is_active() is expected
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError
---
----------------------------------------------------------------------
Ran 1 test in 0.672s
FAILED (failures=1)
test test_sys failed
1 test failed again:
    test_sys
== Tests result: FAILURE then FAILURE ==

This is a build --with-pydebug --disable-gil --enable-experimental-jit=yes-off. An optimized build without pydebug behaves the same way. I am also testing with Python 3.14.

A full log with testinfo: build.log

The same test failure happens both on x86_64 and aarch64 Fedora. This is 3.15.0a2.

CPython versions tested on:

3.15

Operating systems tested on:

Linux

Comece com Lib/test/test_sys.py e TestSysJIT.test_jit_is_active e, em seguida, reproduza a falha usando --with-pydebug --disable-gil --enable-experimental-jit=yes-off. Compare o comportamento relatado em builds freethreading com o estado JIT esperado pelo teste ao longo do loop rastreado e das chamadas ao interpretador. Considera-se concluído quando o teste passa para as configurações de build afetadas nas arquiteturas relatadas.