8000 gh-112087: Make list_{subscript, ass_slice, slice} to be thread-safe by corona10 · Pull Request #115854 · python/cpython · GitHub
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gh-112087: Make list_{subscript, ass_slice, slice} to be thread-safe #115854

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gh-112087: Make list_{subscript, ass_slice, slice} to be thread-safe #115854

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a4bf501
gh-112087: Make list_subscript to be thread-safe
corona10 Feb 21, 2024
ed192d7
Make list_ass_slice to be thread-safe(?)
corona10 Feb 23, 2024
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gh-112087: Make list_subscript to be thread-safe
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@corona10
corona10 committed Feb 21, 2024
commit a4bf5013bb07cc6f626dcf50f93f18f65ddfd4af
89 changes: 60 additions & 29 deletions Objects/listobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -505,6 +505,23 @@ list_item(PyObject *aa, Py_ssize_t i)
return Py_NewRef(a->ob_item[i]);
}

static PyObject *
list_slice_lock_held(PyListObject *a, Py_ssize_t start, Py_ssize_t len)
{
PyListObject *np = (PyListObject *) list_new_prealloc(len);
if (np == NULL) {
return NULL;
}
PyObject **src = a->ob_item + start;
PyObject **dest = np->ob_item;
for (Py_ssize_t i = 0; i < len; i++) {
PyObject *v = src[i];
FT_ATOMIC_STORE_PTR_RELAXED(dest[i], Py_NewRef(v));
}
Py_SET_SIZE(np, len);
return (PyObject *)np;
}

static PyObject *
list_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
{
Expand Down Expand Up @@ -3062,6 +3079,47 @@ static PySequenceMethods list_as_sequence = {
list_inplace_repeat, /* sq_inplace_repeat */
};

static PyObject *
list_slice_step_lock_held(PyListObject *a, Py_ssize_t start, Py_ssize_t step, Py_ssize_t len)
{
PyObject *obj = list_new_prealloc(len);
if (obj == NULL) {
return NULL;
}
PyListObject *np = (PyListObject *)obj;
size_t cur;
Py_ssize_t i;
PyObject **src = a->ob_item;
PyObject **dest = np->ob_item;
for (cur = start, i = 0; i < len;
cur += (size_t)step, i++) {
PyObject *v = src[cur];
FT_ATOMIC_STORE_PTR_RELAXED(dest[i], Py_NewRef(v));
}
Py_SET_SIZE(np, len);
return (PyObject *)np;
}

static PyObject *
list_slice_wrap(PyListObject *aa, Py_ssize_t start, Py_ssize_t stop, Py_ssize_t step)
{
PyObject *res = NULL;
PyListObject *a = (PyListObject *)aa;
Py_BEGIN_CRITICAL_SECTION(a);
< 8000 /td> Py_ssize_t len = PySlice_AdjustIndices(Py_SIZE(a), &start, &stop, step);
if (len <= 0) {
res = PyList_New(0);
}
else if (step == 1) {
res = list_slice_lock_held(a, start, len);
}
else {
res = list_slice_step_lock_held(a, start, step, len);
}
Py_END_CRITICAL_SECTION();
return res;
}

static PyObject *
list_subscript(PyObject* _self, PyObject* item)
{
Expand All @@ -3076,38 +3134,11 @@ list_subscript(PyObject* _self, PyObject* item)
return list_item((PyObject *)self, i);
}
else if (PySlice_Check(item)) {
Py_ssize_t start, stop, step, slicelength, i;
size_t cur;
PyObject* result;
PyObject* it;
PyObject **src, **dest;

Py_ssize_t start, stop, step;
if (PySlice_Unpack(item, &start, &stop, &step) < 0) {
return NULL;
}
slicelength = PySlice_AdjustIndices(Py_SIZE(self), &start, &stop,
step);

if (slicelength <= 0) {
return PyList_New(0);
}
else if (step == 1) {
return list_slice(self, start, stop);
}
else {
result = list_new_prealloc(slicelength);
if (!result) return NULL;

src = self->ob_item;
dest = ((PyListObject *)result)->ob_item;
for (cur = start, i = 0; i < slicelength;
cur += (size_t)step, i++) {
it = Py_NewRef(src[cur]);
dest[i] = it;
}
Py_SET_SIZE(result, slicelength);
return result;
}
return list_slice_wrap(self, st 4911 art, stop, step);
}
else {
PyErr_Format(PyExc_TypeError,
Expand Down
0