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[3.13] gh-127020: Make PyCode_GetCode thread-safe for free threading (GH-127043) (GH-127107)

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Some fields in PyCodeObject are lazily initialized. Use atomics and
critical sections to make their initializations and accesses thread-safe.
(cherry picked from commit 3926842117)

Co-authored-by: Sam Gross <colesbury@gmail.com>
This commit is contained in:
Miss Islington (bot) 2024-11-21 17:27:36 +01:00 • committed by GitHub
parent c09366b1fe
commit c74331413e
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GPG key ID: B5690EEEBB952194
3 changed files with 86 additions and 28 deletions
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80
Objects/codeobject.c
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@ -304,21 +304,32 @@ validate_and_copy_tuple(PyObject *tup)
}
static int
init_co_cached(PyCodeObject *self) {
if (self->_co_cached == NULL) {
self->_co_cached = PyMem_New(_PyCoCached, 1);
if (self->_co_cached == NULL) {
PyErr_NoMemory();
return -1;
}
self->_co_cached->_co_code = NULL;
self->_co_cached->_co_cellvars = NULL;
self->_co_cached->_co_freevars = NULL;
self->_co_cached->_co_varnames = NULL;
init_co_cached(PyCodeObject *self)
{
_PyCoCached *cached = FT_ATOMIC_LOAD_PTR(self->_co_cached);
if (cached != NULL) {
return 0;
}
return 0;
Py_BEGIN_CRITICAL_SECTION(self);
cached = self->_co_cached;
if (cached == NULL) {
cached = PyMem_New(_PyCoCached, 1);
if (cached == NULL) {
PyErr_NoMemory();
}
else {
cached->_co_code = NULL;
cached->_co_cellvars = NULL;
cached->_co_freevars = NULL;
cached->_co_varnames = NULL;
FT_ATOMIC_STORE_PTR(self->_co_cached, cached);
}
}
Py_END_CRITICAL_SECTION();
return cached != NULL ? 0 : -1;
}
/******************
* _PyCode_New()
******************/
@ -1544,16 +1555,21 @@ get_cached_locals(PyCodeObject *co, PyObject **cached_field,
{
assert(cached_field != NULL);
assert(co->_co_cached != NULL);
if (*cached_field != NULL) {
return Py_NewRef(*cached_field);
PyObject *varnames = FT_ATOMIC_LOAD_PTR(*cached_field);
if (varnames != NULL) {
return Py_NewRef(varnames);
}
assert(*cached_field == NULL);
PyObject *varnames = get_localsplus_names(co, kind, num);
Py_BEGIN_CRITICAL_SECTION(co);
varnames = *cached_field;
if (varnames == NULL) {
return NULL;
varnames = get_localsplus_names(co, kind, num);
if (varnames != NULL) {
FT_ATOMIC_STORE_PTR(*cached_field, varnames);
}
}
*cached_field = Py_NewRef(varnames);
return varnames;
Py_END_CRITICAL_SECTION();
return Py_XNewRef(varnames);
}
PyObject *
@ -1652,18 +1668,26 @@ _PyCode_GetCode(PyCodeObject *co)
if (init_co_cached(co)) {
return NULL;
}
if (co->_co_cached->_co_code != NULL) {
return Py_NewRef(co->_co_cached->_co_code);
_PyCoCached *cached = co->_co_cached;
PyObject *code = FT_ATOMIC_LOAD_PTR(cached->_co_code);
if (code != NULL) {
return Py_NewRef(code);
}
PyObject *code = PyBytes_FromStringAndSize((const char *)_PyCode_CODE(co),
_PyCode_NBYTES(co));
Py_BEGIN_CRITICAL_SECTION(co);
code = cached->_co_code;
if (code == NULL) {
return NULL;
code = PyBytes_FromStringAndSize((const char *)_PyCode_CODE(co),
_PyCode_NBYTES(co));
if (code != NULL) {
deopt_code(co, (_Py_CODEUNIT *)PyBytes_AS_STRING(code));
assert(cached->_co_code == NULL);
FT_ATOMIC_STORE_PTR(cached->_co_code, code);
}
}
deopt_code(co, (_Py_CODEUNIT *)PyBytes_AS_STRING(code));
assert(co->_co_cached->_co_code == NULL);
co->_co_cached->_co_code = Py_NewRef(code);
return code;
Py_END_CRITICAL_SECTION();
return Py_XNewRef(code);
}
PyObject *