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gh-112087: Make PyList_{Append,Size,GetSlice} to be thread-safe #114651

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Merged
merged 7 commits into from
Jan 31, 2024
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gh-112087: Make PyList_{Append,Size,GetSlice} to be thread-safe #114651

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393cbef
gh-112087: Make PyList_{Append,GetItem,Size,GetSlice} to be thread-safe
corona10 Jan 27, 2024
df1661d
Fix compiler warn
corona10 Jan 27, 2024
6f37b61
nit
corona10 Jan 27, 2024
f67f936
fix
corona10 Jan 27, 2024
ba74dc5
Improve _PyList_AppendTakeRef
corona10 Jan 27, 2024
9075e61
nit
corona10 Jan 27, 2024
553db97
Address code review
corona10 Jan 30, 2024
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3 changes: 2 additions & 1 deletion Include/internal/pycore_list.h
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Original file line number Diff line number Diff line change
Expand Up @@ -24,12 +24,13 @@ extern void _PyList_Fini(_PyFreeListState *);
extern int
_PyList_AppendTakeRefListResize(PyListObject *self, PyObject *newitem);

// In free-threaded build: self should be locked by the caller, if it should be thread-safe.
static inline int
_PyList_AppendTakeRef(PyListObject *self, PyObject *newitem)
{
assert(self != NULL && newitem != NULL);
assert(PyList_Check(self));
Py_ssize_t len = PyList_GET_SIZE(self);
Py_ssize_t len = Py_SIZE(self);
Py_ssize_t allocated = self->allocated;
assert((size_t)len + 1 < PY_SSIZE_T_MAX);
if (allocated > len) {
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4 changes: 4 additions & 0 deletions Include/object.h
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Expand Up @@ -428,7 +428,11 @@ static inline void Py_SET_TYPE(PyObject *ob, PyTypeObject *type) {
static inline void Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size) {
assert(ob->ob_base.ob_type != &PyLong_Type);
assert(ob->ob_base.ob_type != &PyBool_Type);
#ifdef Py_GIL_DISABLED
_Py_atomic_store_ssize_relaxed(&ob->ob_size, size);
#else
ob->ob_size = size;
#endif
}
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
# define Py_SET_SIZE(ob, size) Py_SET_SIZE(_PyVarObject_CAST(ob), (size))
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22 changes: 15 additions & 7 deletions Objects/listobject.c
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Expand Up @@ -30,7 +30,6 @@ get_list_state(void)
}
#endif


/* Ensure ob_item has room for at least newsize elements, and set
* ob_size to newsize. If newsize > ob_size on entry, the content
* of the new slots at exit is undefined heap trash; it's the caller's
Expand Down Expand Up @@ -221,8 +220,9 @@ PyList_Size(PyObject *op)
PyErr_BadInternalCall();
return -1;
}
else
return Py_SIZE(op);
else {
return PyList_GET_SIZE(op);
}
}

static inline int
Expand Down Expand Up @@ -328,7 +328,7 @@ PyList_Insert(PyObject *op, Py_ssize_t where, PyObject *newitem)
int
_PyList_AppendTakeRefListResize(PyListObject *self, PyObject *newitem)
{
Py_ssize_t len = PyList_GET_SIZE(self);
Py_ssize_t len = Py_SIZE(self);
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@corona10 corona10 Jan 27, 2024 •
edited
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It is only called by _PyList_AppendTakeRef, so it's safe.

assert(self->allocated == -1 || self->allocated == len);
if (list_resize(self, len + 1) < 0) {
Py_DECREF(newitem);
Expand All @@ -342,7 +342,11 @@ int
PyList_Append(PyObject *op, PyObject *newitem)
{
if (PyList_Check(op) && (newitem != NULL)) {
return _PyList_AppendTakeRef((PyListObject *)op, Py_NewRef(newitem));
int ret;
Py_BEGIN_CRITICAL_SECTION(op);
ret = _PyList_AppendTakeRef((PyListObject *)op, Py_NewRef(newitem));
Py_END_CRITICAL_SECTION();
return ret;
}
PyErr_BadInternalCall();
return -1;
Expand Down Expand Up @@ -473,7 +477,7 @@ static PyObject *
list_item(PyObject *aa, Py_ssize_t i)
{
PyListObject *a = (PyListObject *)aa;
if (!valid_index(i, Py_SIZE(a))) {
if (!valid_index(i, PyList_GET_SIZE(a))) {
PyErr_SetObject(PyExc_IndexError, &_Py_STR(list_err));
return NULL;
}
Expand Down Expand Up @@ -511,6 +515,8 @@ PyList_GetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
PyErr_BadInternalCall();
return NULL;
}
PyObject *ret;
Py_BEGIN_CRITICAL_SECTION(a);
if (ilow < 0) {
ilow = 0;
}
Expand All @@ -523,7 +529,9 @@ PyList_GetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
else if (ihigh > Py_SIZE(a)) {
ihigh = Py_SIZE(a);
}
return list_slice((PyListObject *)a, ilow, ihigh);
ret = list_slice((PyListObject *)a, ilow, ihigh);
Py_END_CRITICAL_SECTION();
return ret;
}

static PyObject *
Expand Down