commit 0749244d13412d7cb5b53d834f586f2198f5b9a6
Author: Brett Simmers <swtaarrs@users.noreply.github.com>
Date:   Tue Feb 20 06:57:48 2024 -0800

    gh-112175: Add `eval_breaker` to `PyThreadState` (#115194)

    This change adds an `eval_breaker` field to `PyThreadState`. The primary
    motivation is for performance in free-threaded builds: with thread-local eval
    breakers, we can stop a specific thread (e.g., for an async exception) without
    interrupting other threads.

    The source of truth for the global instrumentation version is stored in the
    `instrumentation_version` field in PyInterpreterState. Threads usually read the
    version from their local `eval_breaker`, where it continues to be colocated
    with the eval breaker bits.

% git clone https://github.com/nedbat/coveragepy
% cd coveragepy
% export COVERAGE_ANYPY=/path/to/your/python3
% pip install tox
% tox -qre anypy -- -n 0 -vvv -k test_multiprocessing_simple
=== CPython 3.13.0a4+ (rev 0749244d13) with C tracer (.tox/anypy/bin/python) ===
===================================================================== test session starts ======================================================================
platform darwin -- Python 3.13.0a4+, pytest-8.0.1, pluggy-1.4.0 -- /Users/ned/coverage/trunk/.tox/anypy/bin/python
cachedir: .tox/anypy/.pytest_cache
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase(PosixPath('/Users/ned/coverage/trunk/.hypothesis/examples'))
rootdir: /Users/ned/coverage/trunk
configfile: pyproject.toml
plugins: flaky-3.7.0, xdist-3.5.0, hypothesis-6.98.9
collected 1386 items / 1384 deselected / 2 selected
run-last-failure: no previously failed tests, not deselecting items.

tests/test_concurrency.py::MultiprocessingTest::test_multiprocessing_simple[fork] PASSED                                                                 [ 50%]
tests/test_concurrency.py::MultiprocessingTest::test_multiprocessing_simple[spawn] PASSED                                                                [100%]

============================================================== 2 passed, 1384 deselected in 3.37s ==============================================================
=== CPython 3.13.0a4+ (rev 0749244d13) with sys.monitoring (.tox/anypy/bin/python) ===
===================================================================== test session starts ======================================================================
platform darwin -- Python 3.13.0a4+, pytest-8.0.1, pluggy-1.4.0 -- /Users/ned/coverage/trunk/.tox/anypy/bin/python
cachedir: .tox/anypy/.pytest_cache
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase(PosixPath('/Users/ned/coverage/trunk/.hypothesis/examples'))
rootdir: /Users/ned/coverage/trunk
configfile: pyproject.toml
plugins: flaky-3.7.0, xdist-3.5.0, hypothesis-6.98.9
collected 1386 items / 1384 deselected / 2 selected
run-last-failure: no previously failed tests, not deselecting items.

tests/test_concurrency.py::MultiprocessingTest::test_multiprocessing_simple[fork] PASSED                                                                 [ 50%]
tests/test_concurrency.py::MultiprocessingTest::test_multiprocessing_simple[spawn]