https://github.com/python/cpython/commit/ec46a55d63eaf015c2cd544b8c727ed7cbb81d33 commit: ec46a55d63eaf015c2cd544b8c727ed7cbb81d33 branch: main author: Pieter Eendebak <pieter.eende...@gmail.com> committer: kumaraditya303 <kumaradi...@python.org> date: 2025-03-14T00:14:05+05:30 summary:
gh-121464: Make concurrent iteration over enumerate safe under free-threading (#125734) files: A Lib/test/test_free_threading/test_enumerate.py A Misc/NEWS.d/next/Core_and_Builtins/2024-10-19-20-22-19.gh-issue-121464.IHwfpK.rst M Objects/enumobject.c diff --git a/Lib/test/test_free_threading/test_enumerate.py b/Lib/test/test_free_threading/test_enumerate.py new file mode 100644 index 00000000000000..d23f5e9529f4c2 --- /dev/null +++ b/Lib/test/test_free_threading/test_enumerate.py @@ -0,0 +1,38 @@ +import unittest +import sys +from threading import Thread, Barrier + +from test.support import threading_helper + +threading_helper.requires_working_threading(module=True) + +class EnumerateThreading(unittest.TestCase): + + @threading_helper.reap_threads + def test_threading(self): + number_of_threads = 10 + number_of_iterations = 8 + n = 100 + start = sys.maxsize - 40 + barrier = Barrier(number_of_threads) + def work(enum): + barrier.wait() + while True: + try: + _ = next(enum) + except StopIteration: + break + + for it in range(number_of_iterations): + enum = enumerate(tuple(range(start, start + n))) + worker_threads = [] + for ii in range(number_of_threads): + worker_threads.append( + Thread(target=work, args=[enum])) + with threading_helper.start_threads(worker_threads): + pass + + barrier.reset() + +if __name__ == "__main__": + unittest.main() diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2024-10-19-20-22-19.gh-issue-121464.IHwfpK.rst b/Misc/NEWS.d/next/Core_and_Builtins/2024-10-19-20-22-19.gh-issue-121464.IHwfpK.rst new file mode 100644 index 00000000000000..6bf031c9cd7904 --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2024-10-19-20-22-19.gh-issue-121464.IHwfpK.rst @@ -0,0 +1 @@ +Make concurrent iterations over the same :func:`enumerate` iterator safe under free-threading. See `Strategy for Iterators in Free Threading <https://github.com/python/cpython/issues/124397>`_. diff --git a/Objects/enumobject.c b/Objects/enumobject.c index 17510b29ee70b5..cbe91eec114230 100644 --- a/Objects/enumobject.c +++ b/Objects/enumobject.c @@ -171,32 +171,45 @@ enum_traverse(PyObject *op, visitproc visit, void *arg) return 0; } +// increment en_longindex with lock held, return the next index to be used +// or NULL on error +static inline PyObject * +increment_longindex_lock_held(enumobject *en) +{ + PyObject *next_index = en->en_longindex; + if (next_index == NULL) { + next_index = PyLong_FromSsize_t(PY_SSIZE_T_MAX); + if (next_index == NULL) { + return NULL; + } + } + assert(next_index != NULL); + PyObject *stepped_up = PyNumber_Add(next_index, en->one); + if (stepped_up == NULL) { + return NULL; + } + en->en_longindex = stepped_up; + return next_index; +} + static PyObject * enum_next_long(enumobject *en, PyObject* next_item) { PyObject *result = en->en_result; PyObject *next_index; - PyObject *stepped_up; PyObject *old_index; PyObject *old_item; - if (en->en_longindex == NULL) { - en->en_longindex = PyLong_FromSsize_t(PY_SSIZE_T_MAX); - if (en->en_longindex == NULL) { - Py_DECREF(next_item); - return NULL; - } - } - next_index = en->en_longindex; - assert(next_index != NULL); - stepped_up = PyNumber_Add(next_index, en->one); - if (stepped_up == NULL) { + + Py_BEGIN_CRITICAL_SECTION(en); + next_index = increment_longindex_lock_held(en); + Py_END_CRITICAL_SECTION(); + if (next_index == NULL) { Py_DECREF(next_item); return NULL; } - en->en_longindex = stepped_up; - if (Py_REFCNT(result) == 1) { + if (_PyObject_IsUniquelyReferenced(result)) { Py_INCREF(result); old_index = PyTuple_GET_ITEM(result, 0); old_item = PyTuple_GET_ITEM(result, 1); @@ -237,17 +250,18 @@ enum_next(PyObject *op) if (next_item == NULL) return NULL; - if (en->en_index == PY_SSIZE_T_MAX) + Py_ssize_t en_index = FT_ATOMIC_LOAD_SSIZE_RELAXED(en->en_index); + if (en_index == PY_SSIZE_T_MAX) return enum_next_long(en, next_item); - next_index = PyLong_FromSsize_t(en->en_index); + next_index = PyLong_FromSsize_t(en_index); if (next_index == NULL) { Py_DECREF(next_item); return NULL; } - en->en_index++; + FT_ATOMIC_STORE_SSIZE_RELAXED(en->en_index, en_index + 1); - if (Py_REFCNT(result) == 1) { + if (_PyObject_IsUniquelyReferenced(result)) { Py_INCREF(result); old_index = PyTuple_GET_ITEM(result, 0); old_item = PyTuple_GET_ITEM(result, 1); @@ -277,10 +291,14 @@ static PyObject * enum_reduce(PyObject *op, PyObject *Py_UNUSED(ignored)) { enumobject *en = _enumobject_CAST(op); + PyObject *result; + Py_BEGIN_CRITICAL_SECTION(en); if (en->en_longindex != NULL) - return Py_BuildValue("O(OO)", Py_TYPE(en), en->en_sit, en->en_longindex); + result = Py_BuildValue("O(OO)", Py_TYPE(en), en->en_sit, en->en_longindex); else - return Py_BuildValue("O(On)", Py_TYPE(en), en->en_sit, en->en_index); + result = Py_BuildValue("O(On)", Py_TYPE(en), en->en_sit, en->en_index); + Py_END_CRITICAL_SECTION(); + return result; } PyDoc_STRVAR(reduce_doc, "Return state information for pickling."); _______________________________________________ Python-checkins mailing list -- python-checkins@python.org To unsubscribe send an email to python-checkins-le...@python.org https://mail.python.org/mailman3/lists/python-checkins.python.org/ Member address: arch...@mail-archive.com
