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Merged
corona10 merged 12 commits into from
Mar 5, 2024
Merged

gh-112087: Make list_{slice, ass_slice, subscript} to be threadsafe #116233

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d9ffc53
gh-112087: Make list_{slice, ass_slice, subscript} to be threadsafe
corona10 Mar 2, 2024
cab2d99
Remove unnecessary atomic operations
corona10 Mar 4, 2024
8b0120d
Update
corona10 Mar 4, 2024
1e19253
Address code review
corona10 Mar 5, 2024
c25ca79
nit
corona10 Mar 5, 2024
1ed3329
Change name
corona10 Mar 5, 2024
033c141
Fix
corona10 Mar 5, 2024
12529a8
Remove inline
corona10 Mar 5, 2024
3335211
fix
corona10 Mar 5, 2024
11b3017
Address code review
corona10 Mar 5, 2024
9ac76ca
Address code review
corona10 Mar 5, 2024
6c037d4
Add test case
corona10 Mar 5, 2024
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5 changes: 5 additions & 0 deletions Lib/test/test_list.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -96,6 +96,11 @@ def imul(a, b): a *= b
self.assertRaises((MemoryError, OverflowError), mul, lst, n)
self.assertRaises((MemoryError, OverflowError), imul, lst, n)

def test_empty_slice(self):
x = []
x[:] = x
self.assertEqual(x, [])

def test_list_resize_overflow(self):
# gh-97616: test new_allocated * sizeof(PyObject*) overflow
# check in list_resize()
Expand Down
132 changes: 82 additions & 50 deletions Objects/listobject.c
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Original file line numberDiff line numberDiff line change
Expand Up@@ -515,7 +515,7 @@ list_item(PyObject *aa, Py_ssize_t i)
}

static PyObject *
list_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
list_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
{
PyListObject *np;
PyObject **src, **dest;
Expand DownExpand Up@@ -559,7 +559,7 @@ PyList_GetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
else if (ihigh > Py_SIZE(a)){
ihigh = Py_SIZE(a);
}
ret = list_slice((PyListObject *)a, ilow, ihigh);
ret = list_slice_lock_held((PyListObject *)a, ilow, ihigh);
Py_END_CRITICAL_SECTION();
return ret;
}
Expand All@@ -584,13 +584,13 @@ list_concat_lock_held(PyListObject *a, PyListObject *b)
dest = np->ob_item;
for (i = 0; i < Py_SIZE(a); i++){
PyObject *v = src[i];
FT_ATOMIC_STORE_PTR_RELAXED(dest[i], Py_NewRef(v));
dest[i] = Py_NewRef(v);
}
src = b->ob_item;
dest = np->ob_item + Py_SIZE(a);
for (i = 0; i < Py_SIZE(b); i++){
PyObject *v = src[i];
FT_ATOMIC_STORE_PTR_RELAXED(dest[i], Py_NewRef(v));
dest[i] = Py_NewRef(v);
}
Py_SET_SIZE(np, size);
return (PyObject *)np;
Expand DownExpand Up@@ -636,15 +636,15 @@ list_repeat_lock_held(PyListObject *a, Py_ssize_t n)
_Py_RefcntAdd(elem, n);
PyObject **dest_end = dest + output_size;
while (dest < dest_end){
FT_ATOMIC_STORE_PTR_RELAXED(*dest++, elem);
*dest++ = elem;
}
}
else{
PyObject **src = a->ob_item;
PyObject **src_end = src + input_size;
while (src < src_end){
_Py_RefcntAdd(*src, n);
FT_ATOMIC_STORE_PTR_RELAXED(*dest++, *src++);
*dest++ = *src++;
}

_Py_memory_repeat((char *)np->ob_item, sizeof(PyObject *)*output_size,
Expand DownExpand Up@@ -718,7 +718,7 @@ list_clear_slot(PyObject *self)
* guaranteed the call cannot fail.
*/
static int
list_ass_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
list_ass_slice_lock_held(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
{
/* Because [X]DECREF can recursively invoke list operations on
this list, we must postpone all [X]DECREF activity until
Expand All@@ -741,15 +741,6 @@ list_ass_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
if (v == NULL)
n = 0;
else{
if (a == b){
/* Special case "a[i:j] = a" -- copy b first */
v = list_slice(b, 0, Py_SIZE(b));
if (v == NULL)
return result;
result = list_ass_slice(a, ilow, ihigh, v);
Py_DECREF(v);
return result;
}
v_as_SF = PySequence_Fast(v, "can only assign an iterable");
if(v_as_SF == NULL)
goto Error;
Expand DownExpand Up@@ -823,6 +814,34 @@ list_ass_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
#undef b
}

static int
list_ass_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
{
int ret;
if (a == (PyListObject *)v){
Py_BEGIN_CRITICAL_SECTION(a);
Py_ssize_t n = PyList_GET_SIZE(a);
PyObject *copy = list_slice_lock_held(a, 0, n);
if (copy == NULL){
return -1;
}
ret = list_ass_slice_lock_held(a, ilow, ihigh, copy);
Py_DECREF(copy);
Py_END_CRITICAL_SECTION();
}
else if (v != NULL && PyList_CheckExact(v)){
Py_BEGIN_CRITICAL_SECTION2(a, v);
ret = list_ass_slice_lock_held(a, ilow, ihigh, v);
Py_END_CRITICAL_SECTION2();
}
else{
Py_BEGIN_CRITICAL_SECTION(a);
ret = list_ass_slice_lock_held(a, ilow, ihigh, v);
Py_END_CRITICAL_SECTION();
}
return ret;
}

int
PyList_SetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
{
Expand DownExpand Up@@ -956,7 +975,7 @@ static PyObject *
list_copy_impl(PyListObject *self)
/*[clinic end generated code: output=ec6b72d6209d418e input=81c54b0c7bb4f73d]*/
{
return list_slice(self, 0, Py_SIZE(self));
return list_slice_lock_held(self, 0, Py_SIZE(self));
}

/*[clinic input]
Expand DownExpand Up@@ -2884,8 +2903,7 @@ list_remove_impl(PyListObject *self, PyObject *value)
int cmp = PyObject_RichCompareBool(obj, value, Py_EQ);
Py_DECREF(obj);
if (cmp > 0){
if (list_ass_slice(self, i, i+1,
(PyObject *)NULL) == 0)
if (list_ass_slice_lock_held(self, i, i+1, NULL) == 0)
Py_RETURN_NONE;
return NULL;
}
Expand DownExpand Up@@ -3085,6 +3103,45 @@ static PySequenceMethods list_as_sequence ={
list_inplace_repeat, /* sq_inplace_repeat */
};

static inline PyObject *
list_slice_step_lock_held(PyListObject *a, Py_ssize_t start, Py_ssize_t step, Py_ssize_t len)
{
PyListObject *np = (PyListObject *)list_new_prealloc(len);
if (np == NULL){
return NULL;
}
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];
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;
Py_BEGIN_CRITICAL_SECTION(aa);
Py_ssize_t len = PySlice_AdjustIndices(Py_SIZE(aa), &start, &stop, step);
if (len <= 0){
res = PyList_New(0);
}
else if (step == 1){
res = list_slice_lock_held(aa, start, stop);
}
else{
res = list_slice_step_lock_held(aa, start, step, len);
}
Py_END_CRITICAL_SECTION();
return res;
}

static PyObject *
list_subscript(PyObject* _self, PyObject* item)
{
Expand All@@ -3099,38 +3156,11 @@ 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, start, stop, step);
}
else{
PyErr_Format(PyExc_TypeError,
Expand DownExpand Up@@ -3241,8 +3271,10 @@ list_ass_subscript(PyObject* _self, PyObject* item, PyObject* value)

/* protect against a[::-1] = a */
if (self == (PyListObject*)value){
seq = list_slice((PyListObject*)value, 0,
PyList_GET_SIZE(value));
Py_BEGIN_CRITICAL_SECTION(value);
seq = list_slice_lock_held((PyListObject*)value, 0,
Py_SIZE(value));
Py_END_CRITICAL_SECTION();
}
else{
seq = PySequence_Fast(value,
Expand Down