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gh-128182: Add per-object memory access synchronization to ctypes #128490

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Merged
encukou merged 24 commits into from
Jan 13, 2025
Merged

gh-128182: Add per-object memory access synchronization to ctypes #128490

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3bb21ff
Lock pointer reads and writes in ctypes.
ZeroIntensity Jan 4, 2025
8c4c49a
Add a test.
ZeroIntensity Jan 4, 2025
da293c1
Fix the test.
ZeroIntensity Jan 4, 2025
d01b757
Add blurb.
ZeroIntensity Jan 4, 2025
8bb980f
Add a lock for generic helper functions.
ZeroIntensity Jan 4, 2025
d60f2e2
Add documentation note.
ZeroIntensity Jan 4, 2025
de4c4ea
Fix compiler warning on GIL-ful builds.
ZeroIntensity Jan 4, 2025
23d8e21
Fix MSVC compiler warnings.
ZeroIntensity Jan 4, 2025
bdee2b2
Fix MSVC compiler warnings (actually this time)
ZeroIntensity Jan 4, 2025
9f272d9
Apply suggestions from code review
ZeroIntensity Jan 6, 2025
32a885f
Fix Sphinx code block.
ZeroIntensity Jan 6, 2025
1c92b4b
Flatten call to PyUnicode_AsWideChar
ZeroIntensity Jan 6, 2025
ff34cc2
Fix lock.
ZeroIntensity Jan 6, 2025
804f1b6
Fix indentation.
ZeroIntensity Jan 6, 2025
bae3c5b
Revert "Flatten call to PyUnicode_AsWideChar"
ZeroIntensity Jan 6, 2025
d720d9a
Properly flatten call to PyUnicode_AsWideChar
ZeroIntensity Jan 6, 2025
04b3252
Fix indentation.
ZeroIntensity Jan 6, 2025
6401bbc
Clarify comment
ZeroIntensity Jan 6, 2025
9d35e86
Switch to critical sections.
ZeroIntensity Jan 8, 2025
ce94234
Update test_arrays.py
ZeroIntensity Jan 9, 2025
d6a4bc8
Update Doc/library/ctypes.rst
ZeroIntensity Jan 9, 2025
5a4c1d6
Update Modules/_ctypes/_ctypes.c
ZeroIntensity Jan 9, 2025
774a6ec
Update Modules/_ctypes/_ctypes.c
ZeroIntensity Jan 9, 2025
c8f2cd3
Remove silly seealso.
ZeroIntensity Jan 10, 2025
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@ZeroIntensity
ZeroIntensity committed Jan 8, 2025
commit 9d35e86f68fc8d4fbccb2660ea9899d875e5c8e8
55 changes: 35 additions & 20 deletions Modules/_ctypes/_ctypes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1443,9 +1443,9 @@ CharArray_set_raw(CDataObject *self, PyObject *value, void *Py_UNUSED(ignored))
static PyObject *
CharArray_get_raw(CDataObject *self, void *Py_UNUSED(ignored))
{
PyObject *res;
LOCK_PTR(self);
// XXX Is it possible that PyBytes_FromStringAndSize is re-entrant?
PyObject *res = PyBytes_FromStringAndSize(self->b_ptr, self->b_size);
res = PyBytes_FromStringAndSize(self->b_ptr, self->b_size);
UNLOCK_PTR(self);
return res;
}
Expand All @@ -1454,12 +1454,13 @@ static PyObject *
CharArray_get_value(CDataObject *self, void *Py_UNUSED(ignored))
{
Py_ssize_t i;
PyObject *res;
LOCK_PTR(self);
char *ptr = self->b_ptr;
for (i = 0; i < self->b_size; ++i)
if (*ptr++ == '\0')
break;
PyObject *res = PyBytes_FromStringAndSize(self->b_ptr, i);
res = PyBytes_FromStringAndSize(self->b_ptr, i);
UNLOCK_PTR(self);
return res;
}
Expand Down Expand Up @@ -1514,12 +1515,13 @@ static PyObject *
WCharArray_get_value(CDataObject *self, void *Py_UNUSED(ignored))
{
Py_ssize_t i;
PyObject *res;
wchar_t *ptr = (wchar_t *)self->b_ptr;
LOCK_PTR(self);
for (i = 0; i < self->b_size/(Py_ssize_t)sizeof(wchar_t); ++i)
if (*ptr++ == (wchar_t)0)
break;
PyObject *res = PyUnicode_FromWideChar((wchar_t *)self->b_ptr, i);
res = PyUnicode_FromWideChar((wchar_t *)self->b_ptr, i);
UNLOCK_PTR(self);
return res;
}
Expand Down Expand Up @@ -1551,8 +1553,9 @@ WCharArray_set_value(CDataObject *self, PyObject *value, void *Py_UNUSED(ignored
PyErr_SetString(PyExc_ValueError, "string too long");
return -1;
}
int rc;
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LOCK_PTR(self);
int rc = PyUnicode_AsWideChar(value, (wchar_t *)self->b_ptr, size);
rc = PyUnicode_AsWideChar(value, (wchar_t *)self->b_ptr, size);
UNLOCK_PTR(self);
return rc < 0 ? -1 : 0;
}
Expand Down Expand Up @@ -3029,8 +3032,9 @@ PyCData_reduce_impl(PyObject *myself, PyTypeObject *cls)
if (dict == NULL) {
return NULL;
}
PyObject *bytes;
LOCK_PTR(self);
PyObject *bytes = PyBytes_FromStringAndSize(self->b_ptr, self->b_size);
bytes = PyBytes_FromStringAndSize(self->b_ptr, self->b_size);
UNLOCK_PTR(self);
return Py_BuildValue("O(O(NN))", st->_unpickle, Py_TYPE(myself), dict,
bytes);
Expand Down Expand Up @@ -3245,8 +3249,9 @@ PyCData_get(ctypes_state *st, PyObject *type, GETFUNC getfunc, PyObject *src,
CDataObject *cdata = (CDataObject *)src;
#endif
if (getfunc) {
PyObject *res;
LOCK_PTR(cdata);
PyObject *res = getfunc(adr, size);
res = getfunc(adr, size);
UNLOCK_PTR(cdata);
return res;
}
Expand All @@ -3256,8 +3261,9 @@ PyCData_get(ctypes_state *st, PyObject *type, GETFUNC getfunc, PyObject *src,
return NULL;
}
if (info && info->getfunc && !_ctypes_simple_instance(st, type)) {
PyObject *res;
LOCK_PTR(cdata);
PyObject *res = info->getfunc(adr, size);
res = info->getfunc(adr, size);
UNLOCK_PTR(cdata);
return res;
}
Expand All @@ -3276,8 +3282,9 @@ _PyCData_set(ctypes_state *st,
int err;

if (setfunc) {
PyObject *res;
LOCK_PTR(dst);
PyObject *res = setfunc(ptr, value, size);
res = setfunc(ptr, value, size);
UNLOCK_PTR(dst);
return res;
}
Expand All @@ -3287,8 +3294,9 @@ _PyCData_set(ctypes_state *st,
return NULL;
}
if (info && info->setfunc) {
PyObject *res;
LOCK_PTR(dst);
PyObject *res = info->setfunc(ptr, value, size);
res = info->setfunc(ptr, value, size);
UNLOCK_PTR(dst);
return res;
}
Expand Down Expand Up @@ -3932,7 +3940,8 @@ PyCFuncPtr_FromDll(PyTypeObject *type, PyObject *args, PyObject *kwds)

self->paramflags = Py_XNewRef(paramflags);

// No other threads can have this object
// No other threads can have this object, no need to
// lock it.
*(void **)self->b_ptr = address;
Py_INCREF(dll);
Py_DECREF(ftuple);
Expand Down Expand Up @@ -4865,9 +4874,10 @@ Array_subscript(PyObject *myself, PyObject *item)
if (slicelen <= 0)
return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
if (step == 1) {
PyObject *res;
LOCK_PTR(self);
PyObject *res = PyBytes_FromStringAndSize(ptr + start,
slicelen);
res = PyBytes_FromStringAndSize(ptr + start,
slicelen);
UNLOCK_PTR(self);
return res;
}
Expand All @@ -4894,8 +4904,9 @@ Array_subscript(PyObject *myself, PyObject *item)
if (slicelen <= 0)
return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
if (step == 1) {
PyObject *res;
LOCK_PTR(self);
PyObject *res = PyUnicode_FromWideChar(ptr + start,
res = PyUnicode_FromWideChar(ptr + start,
slicelen);
UNLOCK_PTR(self);
return res;
Expand Down Expand Up @@ -5201,8 +5212,9 @@ Simple_get_value(CDataObject *self, void *Py_UNUSED(ignored))
}
assert(info); /* Cannot be NULL for CDataObject instances */
assert(info->getfunc);
PyObject *res;
LOCK_PTR(self);
PyObject *res = info->getfunc(self->b_ptr, self->b_size);
res = info->getfunc(self->b_ptr, self->b_size);
UNLOCK_PTR(self);
return res;
}
Expand Down Expand Up @@ -5240,8 +5252,9 @@ static PyMethodDef Simple_methods[] = {

static int Simple_bool(CDataObject *self)
{
int cmp;
LOCK_PTR(self);
int cmp = memcmp(self->b_ptr, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", self->b_size);
cmp = memcmp(self->b_ptr, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", self->b_size);
UNLOCK_PTR(self);
return cmp;
}
Expand Down Expand Up @@ -5571,9 +5584,10 @@ Pointer_subscript(PyObject *myself, PyObject *item)
if (len <= 0)
return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
if (step == 1) {
PyObject *res;
LOCK_PTR(self);
PyObject *res = PyBytes_FromStringAndSize(ptr + start,
len);
res = PyBytes_FromStringAndSize(ptr + start,
len);
UNLOCK_PTR(self);
return res;
}
Expand All @@ -5596,9 +5610,10 @@ Pointer_subscript(PyObject *myself, PyObject *item)
if (len <= 0)
return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
if (step == 1) {
PyObject *res;
LOCK_PTR(self);
PyObject *res = PyUnicode_FromWideChar(ptr + start,
len);
res = PyUnicode_FromWideChar(ptr + start,
len);
UNLOCK_PTR(self);
return res;
}
Expand Down
15 changes: 6 additions & 9 deletions Modules/_ctypes/ctypes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -152,9 +152,6 @@ union value {

struct tagCDataObject {
PyObject_HEAD
#ifdef Py_GIL_DISABLED
PyMutex b_ptr_lock;
#endif
char *b_ptr; /* pointer to memory block */
int b_needsfree; /* need _we_ free the memory? */
CDataObject *b_base; /* pointer to base object or NULL */
Expand Down Expand Up @@ -184,9 +181,6 @@ typedef struct {
typedef struct {
/* First part identical to tagCDataObject */
PyObject_HEAD
#ifdef Py_GIL_DISABLED
PyMutex b_ptr_lock;
#endif
char *b_ptr; /* pointer to memory block */
int b_needsfree; /* need _we_ free the memory? */
CDataObject *b_base; /* pointer to base object or NULL */
Expand Down Expand Up @@ -550,9 +544,11 @@ PyStgInfo_Init(ctypes_state *state, PyTypeObject *type)
return info;
}

/* See discussion in gh-128490. The plan here is to eventually use a per-object
* lock rather than a critical section, but that work is for later. */
#ifdef Py_GIL_DISABLED
# define LOCK_PTR(self) PyMutex_Lock(&self->b_ptr_lock)
# define UNLOCK_PTR(self) PyMutex_Unlock(&self->b_ptr_lock)
# define LOCK_PTR(self) Py_BEGIN_CRITICAL_SECTION(self)
# define UNLOCK_PTR(self) Py_END_CRITICAL_SECTION()
#else
# define LOCK_PTR(self)
# define UNLOCK_PTR(self)
Expand All @@ -577,8 +573,9 @@ locked_memcpy_from(void *buf, CDataObject *self, Py_ssize_t size)
static inline void *
locked_deref(CDataObject *self)
{
void *ptr;
LOCK_PTR(self);
void *ptr = *(void **)self->b_ptr;
ptr = *(void **)self->b_ptr;
UNLOCK_PTR(self);
return ptr;
}
Expand Down