analysis of gilstate operations

gistfile1.txt

_PyRuntimeState_GetThreadState()
    _PyRuntime.gilstate.tstate_current                                                                                  <----


_PyRuntimeGILState_GetThreadState()
    _PyRuntime.gilstate.tstate_current                                                                                  <----


_PyRuntimeGILState_SetThreadState(tstate)
    _PyRuntime.gilstate.tstate_current = tstate                                                                         <----


_PyThreadState_GET()
    _PyRuntimeState_GetThreadState()
        ...


_PyInterpreterState_GET()
    tstate = _PyThreadState_GET()
        ...
    _Py_EnsureTstateNotNULL()
    return tstate->interp


_PyGILState_GetInterpreterStateUnsafe()
    _PyRuntime.gilstate.autoInterpreterState                                                                                    <----
    

_PyGILState_GetThisThreadState()
    if _PyRuntime.gilstate.autoInterpreterState:                                                                                <----
        expected = PyThread_tss_get(_PyRuntime.gilstate.autoTSSkey)                                                         <----
    else
        expected = NULL


_PyGILState_NoteThreadState()
    if _PyRuntime.gilstate.autoInterpreterState:                                                                                <----
        if PyThread_tss_get(_PyRuntime.gilstate.autoTSSkey) == NULL:                                                        <----
            PyThread_tss_set(_PyRuntime.gilstate.autoTSSkey, newts)                                                         <----


_PyGILState_SetTstate()
    if _Py_IsMainInterpreter(tstate.interp):
        _PyRuntime.gilstate.autoInterpreterState = tstate.interp                                                                <----
        _PyGILState_NoteThreadState(tstate)
            ...

PyThreadState_IsCurrent(tcur)
    assert(_PyGILState_GetThisThreadState() == tcur)
        ...
    current = (tcur == _PyRuntimeGILState_GetThreadState())
        ...


_PyThreadState_SetCurrent()
    _PyGILState_NoteThreadState()
        ...


_PyThreadState_DeleteCurrent()
    tstate_delete_common()
        if _PyRuntime.gilstate.autoInterpreterState and                                                                         <----
                 PyThread_tss_get(_PyRuntime.gilstate.autoTSSkey) == tstate:                                                <----
            PyThread_tss_set(_PyRuntime.gilstate.autoTSSkey, NULL)                                                          <----


_PyThreadState_Swap()
    _PyRuntimeGILState_GetThreadState()
        ...
    _PyRuntimeGILState_SetThreadState()
        ...


PyEval_SaveThread()
    oldts = _PyThreadState_Swap(NULL)
        ...
    _Py_EnsureTstateNotNULL(oldts)
    assert(gil_created())
        ...
    drop_gil()
        if _PyRuntime.ceval.gil.locked:
            _PyRuntime.ceval.gil.last_holder = tstate
            _PyRuntime.ceval.gil.locked = 1


PyEval_RestoreThread()
    _Py_EnsureTstateNotNULL()
    take_gil()
        ...
    _PyThreadState_Swap()
        ...


Py_BEGIN_ALLOW_THREADS
    PyEval_SaveThread()
        ...


Py_END_ALLOW_THREADS
    PyEval_RestoreThread()
        ...


PyThreadState_New(interp = _PyRuntime.gilstate.autoInterpreterState)                                                            <----
    new_threadstate()
        acquire-head-lock
        | interp.threads.next_unique_id++
        | newts = alloc_threadstate()
        | interp.threads.head = tcur
        | init_threadstate()
        |   tcur.interp = interp
        - release-head-lock
    _PyThreadState_SetCurrent()
        ...


PyGILState_Ensure()
    assert(_PyEval_ThreadsInitialized())
        gil_created()
            actual = (_PyRuntime.ceval.gil.locked >= 0)
    assert(_PyRuntime.gilstate.autoInterpreterState)                                                                            <----
    tcur = PyThread_tss_get(_PyRuntime.gilstate.autoTSSkey)                                                                 <----
    if tcur == NULL:
        tcur = PyThreadState_New(interp = _PyRuntime.gilstate.autoInterpreterState)                                             <----
            ...
        current = False
    else:
        current = PyThreadState_IsCurrent(tcur)
            ...
    return PyGILState_LOCKED if current else PyGILState_UNLOCKED


PyGILState_Release()
    tstate = PyThread_tss_get(_PyRuntime.gilstate.autoTSSkey)                                                               <----
    if PyThreadState_IsCurrent(tstate):
            ...
        --tstate.gilstate_counter
        if tstate.gilstate_counter == 0:
            PyThreadState_Clear(tstate)
            assert(_PyRuntimeGILState_GetThreadState() == tstate)
                ...
            _PyThreadState_DeleteCurrent()
                ...
        elif oldstate == PyGILState_UNLOCKED:
            PyEval_SaveThread()
                ...


###############################################################################

# failing on some buildbots due to https://github.com/python/cpython/pull/99378

test.test_threading.ThreadTests.test_frame_tstate_tracing()
  _testcapi.call_in_temporary_c_thread()
    acquire-start-lock
    acquire-exit-lock
    PyThread_start_new_thread() -> temporary_c_thread()
        _PyThreadState_GET()
            ...
        pthread_create() -> pythread_wrapper() -> temporary_c_thread()
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
            release-start-lock
            PyGILState_Ensure()
                ...
            PyObject_CallNoArgs()
            Py_CLEAR()
            PyGILState_Release()
                ...
            release-exit-lock
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        block-on-start-lock
        Py_BEGIN_ALLOW_THREADS
            ...
        block-on-exit-lock
        Py_END_ALLOW_THREADS
            ...

*******************************************************************************

main
    lock "start"
    lock "stop"
    get _PyRuntime.gilstate.tstate_current (discarded)
    block on "start"

new thread
    release "start"

race
    main
        get _PyRuntime.gilstate.tstate_current -> oldts
        set _PyRuntime.gilstate.tstate_current <- NULL
    new thread
        get _PyRuntime.gilstate.autoInterpreterState (discarded)
        tss-get _PyRuntime.gilstate.autoTSSkey -> tcur
        if tcur == NULL:
            get _PyRuntime.gilstate.autoInterpreterState -> interp
            get _PyRuntime.gilstate.autoInterpreterState (discarded)
            tss-get _PyRuntime.gilstate.autoTSSkey (discarded)
            tss-set _PyRuntime.gilstate.autoTSSkey <- tcur
        else:
            get _PyRuntime.gilstate.autoInterpreterState (discarded)
            tss-get _PyRuntime.gilstate.autoTSSkey (discarded)
            get _PyRuntime.gilstate.tstate_current (discarded)

        <various uses via PyObject_CallNoArgs()>

        tss-get _PyRuntime.gilstate.autoTSSkey -> tstate
        get _PyRuntime.gilstate.tstate_current (discarded)
        get _PyRuntime.gilstate.autoInterpreterState (discarded)
        tss-get _PyRuntime.gilstate.autoTSSkey -> current
        if current == tstate:
            tss-set _PyRuntime.gilstate.autoTSSkey <- NULL
        get _PyRuntime.gilstate.tstate_current -> ,,,
        set _PyRuntime.gilstate.tstate_current <- NULL

main
    block on "stop"
    get _PyRuntime.gilstate.tstate_current (discarded)
    set _PyRuntime.gilstate.tstate_current <- oldts

new thread
    release "stop"

###############################################################################

# failing on some buildbots due to https://github.com/python/cpython/pull/99378

test.test_capi.test_misc.TestThreadState.test_gilstate_ensure_no_deadlock()
    _testcapi._test_thread_state()
        acquire-done-lock
        PyThread_start_new_thread() -> pythread_wrapper() -> _make_call_from_thread()
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
            _make_call()
                PyGILState_Ensure()
                   ...
                PyObject_CallNoArgs()
                PyGILState_Release()
                   ...
            release-done-lock
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        _make_call()
            ...
        Py_BEGIN_ALLOW_THREADS
            ...
        _make_call()
            ...
        block-on-done-lock
        Py_END_ALLOW_THREADS
            ...
        Py_BEGIN_ALLOW_THREADS
            ...
        PyThread_start_new_thread()
        _make_call()
            ...
        block-on-done-lock
        Py_END_ALLOW_THREADS
            ...

*******************************************************************************

...


###############################################################################