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bpo-42639: Move atexit state to PyInterpreterState (GH-23763)
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* Add _PyAtExit_Call() function and remove pyexitfunc and
  pyexitmodule members of PyInterpreterState. The function
  logs atexit callback errors using _PyErr_WriteUnraisableMsg().
* Add _PyAtExit_Init() and _PyAtExit_Fini() functions.
* Remove traverse, clear and free functions of the atexit module.

Co-authored-by: Dong-hee Na <donghee.na@python.org>
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@vstinner @corona10 @adorilson
2 people authored and adorilson committed Mar 11, 2021
1 parent d3ed8d2 commit 44d7e67
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Showing 7 changed files with 101 additions and 113 deletions.
18 changes: 15 additions & 3 deletions Include/internal/pycore_interp.h
View file
Expand Up @@ -159,6 +159,20 @@ struct _Py_exc_state {
};


// atexit state
typedef struct {
PyObject *func;
PyObject *args;
PyObject *kwargs;
} atexit_callback;

struct atexit_state {
atexit_callback **callbacks;
int ncallbacks;
int callback_len;
};


/* interpreter state */

#define _PY_NSMALLPOSINTS 257
Expand Down Expand Up @@ -234,12 +248,10 @@ struct _is {
PyObject *after_forkers_child;
#endif

/* AtExit module */
PyObject *atexit_module;

uint64_t tstate_next_unique_id;

struct _warnings_runtime_state warnings;
struct atexit_state atexit;

PyObject *audit_hooks;

Expand Down
4 changes: 3 additions & 1 deletion Include/internal/pycore_pylifecycle.h
View file
Expand Up @@ -55,6 +55,7 @@ extern PyStatus _PyTypes_Init(void);
extern PyStatus _PyTypes_InitSlotDefs(void);
extern PyStatus _PyImportZip_Init(PyThreadState *tstate);
extern PyStatus _PyGC_Init(PyThreadState *tstate);
extern PyStatus _PyAtExit_Init(PyThreadState *tstate);


/* Various internal finalizers */
Expand Down Expand Up @@ -85,6 +86,7 @@ extern void _PyHash_Fini(void);
extern void _PyTraceMalloc_Fini(void);
extern void _PyWarnings_Fini(PyInterpreterState *interp);
extern void _PyAST_Fini(PyInterpreterState *interp);
extern void _PyAtExit_Fini(PyInterpreterState *interp);

extern PyStatus _PyGILState_Init(PyThreadState *tstate);
extern void _PyGILState_Fini(PyThreadState *tstate);
Expand All @@ -109,7 +111,7 @@ PyAPI_FUNC(void) _PyErr_Display(PyObject *file, PyObject *exception,

PyAPI_FUNC(void) _PyThreadState_DeleteCurrent(PyThreadState *tstate);

extern void _PyAtExit_Call(PyObject *module);
extern void _PyAtExit_Call(PyThreadState *tstate);

#ifdef __cplusplus
}
Expand Down
18 changes: 18 additions & 0 deletions Lib/test/test_atexit.py
View file
Expand Up @@ -170,6 +170,24 @@ def f(msg):
self.assertEqual(res.out.decode().splitlines(), ["two", "one"])
self.assertFalse(res.err)

def test_atexit_instances(self):
# bpo-42639: It is safe to have more than one atexit instance.
code = textwrap.dedent("""
import sys
import atexit as atexit1
del sys.modules['atexit']
import atexit as atexit2
del sys.modules['atexit']
assert atexit2 is not atexit1
atexit1.register(print, "atexit1")
atexit2.register(print, "atexit2")
""")
res = script_helper.assert_python_ok("-c", code)
self.assertEqual(res.out.decode().splitlines(), ["atexit2", "atexit1"])
self.assertFalse(res.err)


@support.cpython_only
class SubinterpreterTest(unittest.TestCase):
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2020-12-09-01-55-10.bpo-42639.5pI5HG.rst
View file
@@ -0,0 +1,3 @@
Make the :mod:`atexit` module state per-interpreter. It is now safe have more
than one :mod:`atexit` module instance.
Patch by Dong-hee Na and Victor Stinner.
150 changes: 53 additions & 97 deletions Modules/atexitmodule.c
View file
Expand Up @@ -7,38 +7,26 @@
*/

#include "Python.h"
#include "pycore_interp.h" // PyInterpreterState.atexit_func
#include "pycore_initconfig.h" // _PyStatus_NO_MEMORY
#include "pycore_interp.h" // PyInterpreterState.atexit
#include "pycore_pystate.h" // _PyInterpreterState_GET

/* ===================================================================== */
/* Callback machinery. */

typedef struct {
PyObject *func;
PyObject *args;
PyObject *kwargs;
} atexit_callback;

struct atexit_state {
atexit_callback **atexit_callbacks;
int ncallbacks;
int callback_len;
};

static inline struct atexit_state*
get_atexit_state(PyObject *module)
get_atexit_state(void)
{
void *state = PyModule_GetState(module);
assert(state != NULL);
return (struct atexit_state *)state;
PyInterpreterState *interp = _PyInterpreterState_GET();
return &interp->atexit;
}


static void
atexit_delete_cb(struct atexit_state *state, int i)
{
atexit_callback *cb = state->atexit_callbacks[i];
state->atexit_callbacks[i] = NULL;
atexit_callback *cb = state->callbacks[i];
state->callbacks[i] = NULL;

Py_DECREF(cb->func);
Py_DECREF(cb->args);
Expand All @@ -53,7 +41,7 @@ atexit_cleanup(struct atexit_state *state)
{
atexit_callback *cb;
for (int i = 0; i < state->ncallbacks; i++) {
cb = state->atexit_callbacks[i];
cb = state->callbacks[i];
if (cb == NULL)
continue;

Expand All @@ -62,25 +50,45 @@ atexit_cleanup(struct atexit_state *state)
state->ncallbacks = 0;
}

/* Installed into pylifecycle.c's atexit mechanism */

static void
atexit_callfuncs(PyObject *module, int ignore_exc)
PyStatus
_PyAtExit_Init(PyThreadState *tstate)
{
assert(!PyErr_Occurred());
struct atexit_state *state = &tstate->interp->atexit;
// _PyAtExit_Init() must only be called once
assert(state->callbacks == NULL);

if (module == NULL) {
return;
state->callback_len = 32;
state->ncallbacks = 0;
state->callbacks = PyMem_New(atexit_callback*, state->callback_len);
if (state->callbacks == NULL) {
return _PyStatus_NO_MEMORY();
}
return _PyStatus_OK();
}


void
_PyAtExit_Fini(PyInterpreterState *interp)
{
struct atexit_state *state = &interp->atexit;
atexit_cleanup(state);
PyMem_Free(state->callbacks);
}


static void
atexit_callfuncs(struct atexit_state *state, int ignore_exc)
{
assert(!PyErr_Occurred());

struct atexit_state *state = get_atexit_state(module);
if (state->ncallbacks == 0) {
return;
}

PyObject *exc_type = NULL, *exc_value, *exc_tb;
for (int i = state->ncallbacks - 1; i >= 0; i--) {
atexit_callback *cb = state->atexit_callbacks[i];
atexit_callback *cb = state->callbacks[i];
if (cb == NULL) {
continue;
}
Expand Down Expand Up @@ -125,15 +133,17 @@ atexit_callfuncs(PyObject *module, int ignore_exc)


void
_PyAtExit_Call(PyObject *module)
_PyAtExit_Call(PyThreadState *tstate)
{
atexit_callfuncs(module, 1);
struct atexit_state *state = &tstate->interp->atexit;
atexit_callfuncs(state, 1);
}


/* ===================================================================== */
/* Module methods. */


PyDoc_STRVAR(atexit_register__doc__,
"register(func, *args, **kwargs) -> func\n\
\n\
Expand Down Expand Up @@ -161,15 +171,15 @@ atexit_register(PyObject *module, PyObject *args, PyObject *kwargs)
return NULL;
}

struct atexit_state *state = get_atexit_state(module);
struct atexit_state *state = get_atexit_state();
if (state->ncallbacks >= state->callback_len) {
atexit_callback **r;
state->callback_len += 16;
r = (atexit_callback**)PyMem_Realloc(state->atexit_callbacks,
sizeof(atexit_callback*) * state->callback_len);
size_t size = sizeof(atexit_callback*) * (size_t)state->callback_len;
r = (atexit_callback**)PyMem_Realloc(state->callbacks, size);
if (r == NULL)
return PyErr_NoMemory();
state->atexit_callbacks = r;
state->callbacks = r;
}

atexit_callback *callback = PyMem_Malloc(sizeof(atexit_callback));
Expand All @@ -185,7 +195,7 @@ atexit_register(PyObject *module, PyObject *args, PyObject *kwargs)
callback->func = Py_NewRef(func);
callback->kwargs = Py_XNewRef(kwargs);

state->atexit_callbacks[state->ncallbacks++] = callback;
state->callbacks[state->ncallbacks++] = callback;

return Py_NewRef(func);
}
Expand All @@ -198,7 +208,8 @@ Run all registered exit functions.");
static PyObject *
atexit_run_exitfuncs(PyObject *module, PyObject *unused)
{
atexit_callfuncs(module, 0);
struct atexit_state *state = get_atexit_state();
atexit_callfuncs(state, 0);
if (PyErr_Occurred()) {
return NULL;
}
Expand All @@ -213,7 +224,7 @@ Clear the list of previously registered exit functions.");
static PyObject *
atexit_clear(PyObject *module, PyObject *unused)
{
atexit_cleanup(get_atexit_state(module));
atexit_cleanup(get_atexit_state());
Py_RETURN_NONE;
}

Expand All @@ -225,41 +236,10 @@ Return the number of registered exit functions.");
static PyObject *
atexit_ncallbacks(PyObject *module, PyObject *unused)
{
struct atexit_state *state = get_atexit_state(module);
struct atexit_state *state = get_atexit_state();
return PyLong_FromSsize_t(state->ncallbacks);
}

static int
atexit_m_traverse(PyObject *module, visitproc visit, void *arg)
{
struct atexit_state *state = (struct atexit_state *)PyModule_GetState(module);
for (int i = 0; i < state->ncallbacks; i++) {
atexit_callback *cb = state->atexit_callbacks[i];
if (cb == NULL)
continue;
Py_VISIT(cb->func);
Py_VISIT(cb->args);
Py_VISIT(cb->kwargs);
}
return 0;
}

static int
atexit_m_clear(PyObject *module)
{
struct atexit_state *state = (struct atexit_state *)PyModule_GetState(module);
atexit_cleanup(state);
return 0;
}

static void
atexit_free(PyObject *module)
{
struct atexit_state *state = (struct atexit_state *)PyModule_GetState(module);
atexit_cleanup(state);
PyMem_Free(state->atexit_callbacks);
}

PyDoc_STRVAR(atexit_unregister__doc__,
"unregister(func) -> None\n\
\n\
Expand All @@ -271,10 +251,10 @@ atexit.register\n\
static PyObject *
atexit_unregister(PyObject *module, PyObject *func)
{
struct atexit_state *state = get_atexit_state(module);
struct atexit_state *state = get_atexit_state();
for (int i = 0; i < state->ncallbacks; i++)
{
atexit_callback *cb = state->atexit_callbacks[i];
atexit_callback *cb = state->callbacks[i];
if (cb == NULL) {
continue;
}
Expand Down Expand Up @@ -305,6 +285,7 @@ static PyMethodDef atexit_methods[] = {
{NULL, NULL} /* sentinel */
};


/* ===================================================================== */
/* Initialization function. */

Expand All @@ -315,37 +296,12 @@ upon normal program termination.\n\
Two public functions, register and unregister, are defined.\n\
");

static int
atexit_exec(PyObject *module)
{
struct atexit_state *state = get_atexit_state(module);
state->callback_len = 32;
state->ncallbacks = 0;
state->atexit_callbacks = PyMem_New(atexit_callback*, state->callback_len);
if (state->atexit_callbacks == NULL) {
return -1;
}

PyInterpreterState *interp = _PyInterpreterState_GET();
interp->atexit_module = module;
return 0;
}

static PyModuleDef_Slot atexit_slots[] = {
{Py_mod_exec, atexit_exec},
{0, NULL}
};

static struct PyModuleDef atexitmodule = {
PyModuleDef_HEAD_INIT,
.m_name = "atexit",
.m_doc = atexit__doc__,
.m_size = sizeof(struct atexit_state),
.m_size = 0,
.m_methods = atexit_methods,
.m_slots = atexit_slots,
.m_traverse = atexit_m_traverse,
.m_clear = atexit_m_clear,
.m_free = (freefunc)atexit_free
};

PyMODINIT_FUNC
Expand Down

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