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gh-112087: Update list_get_item_ref to optimistically avoid locking (gh-116353) 

Co-authored-by: Sam Gross <colesbury@gmail.com>
This commit is contained in:
Donghee Na 2024-03-06 08:21:33 +09:00 committed by GitHub
parent 990a5f17d0
commit d2f1b0eb49
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GPG Key ID: B5690EEEBB952194
1 changed files with 60 additions and 11 deletions
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71
Objects/listobject.c
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@ -233,6 +233,63 @@ valid_index(Py_ssize_t i, Py_ssize_t limit)
return (size_t) i < (size_t) limit;
}
#ifdef Py_GIL_DISABLED
static PyObject *
list_item_impl(PyListObject *self, Py_ssize_t idx)
{
PyObject *item = NULL;
Py_BEGIN_CRITICAL_SECTION(self);
if (!_PyObject_GC_IS_SHARED(self)) {
_PyObject_GC_SET_SHARED(self);
}
Py_ssize_t size = Py_SIZE(self);
if (!valid_index(idx, size)) {
goto exit;
}
item = Py_NewRef(self->ob_item[idx]);
exit:
Py_END_CRITICAL_SECTION();
return item;
}
static inline PyObject*
list_get_item_ref(PyListObject *op, Py_ssize_t i)
{
if (!_Py_IsOwnedByCurrentThread((PyObject *)op) && !_PyObject_GC_IS_SHARED(op)) {
return list_item_impl(op, i);
}
// Need atomic operation for the getting size.
Py_ssize_t size = PyList_GET_SIZE(op);
if (!valid_index(i, size)) {
return NULL;
}
PyObject **ob_item = _Py_atomic_load_ptr(&op->ob_item);
if (ob_item == NULL) {
return NULL;
}
Py_ssize_t cap = _Py_atomic_load_ssize_relaxed(&op->allocated);
assert(cap != -1 && cap >= size);
if (!valid_index(i, cap)) {
return NULL;
}
PyObject *item = _Py_TryXGetRef(&ob_item[i]);
if (item == NULL) {
return list_item_impl(op, i);
}
return item;
}
#else
static inline PyObject*
list_get_item_ref(PyListObject *op, Py_ssize_t i)
{
if (!valid_index(i, Py_SIZE(op))) {
return NULL;
}
return Py_NewRef(PyList_GET_ITEM(op, i));
}
#endif
PyObject *
PyList_GetItem(PyObject *op, Py_ssize_t i)
{
@ -255,21 +312,13 @@ PyList_GetItemRef(PyObject *op, Py_ssize_t i)
PyErr_SetString(PyExc_TypeError, "expected a list");
return NULL;
}
if (!valid_index(i, Py_SIZE(op))) {
PyObject *item = list_get_item_ref((PyListObject *)op, i);
if (item == NULL) {
_Py_DECLARE_STR(list_err, "list index out of range");
PyErr_SetObject(PyExc_IndexError, &_Py_STR(list_err));
return NULL;
}
return Py_NewRef(PyList_GET_ITEM(op, i));
}
static inline PyObject*
list_get_item_ref(PyListObject *op, Py_ssize_t i)
{
if (!valid_index(i, Py_SIZE(op))) {
return NULL;
}
return Py_NewRef(PyList_GET_ITEM(op, i));
return item;
}
int