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gh-91048: fix thread safety for asyncio stack introspection APIs #129399

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merged 2 commits into from
Feb 6, 2025
Merged

gh-91048: fix thread safety for asyncio stack introspection APIs #129399

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37e9a7d
fix thread safety
kumaraditya303 Jan 28, 2025
54bdc3b
Merge branch 'main' into tsafe
kumaraditya303 Jan 31, 2025
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171 changes: 98 additions & 73 deletions Modules/_asynciomodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -549,30 +549,28 @@ future_init(FutureObj *fut, PyObject *loop)
}

static int
future_awaited_by_add(asyncio_state *state, PyObject *fut, PyObject *thing)
future_awaited_by_add(asyncio_state *state, FutureObj *fut, PyObject *thing)
{
if (!TaskOrFuture_Check(state, fut) || !TaskOrFuture_Check(state, thing)) {
// We only want to support native asyncio Futures.
// For further insight see the comment in the Python
// implementation of "future_add_to_awaited_by()".
return 0;
}

FutureObj *_fut = (FutureObj *)fut;
_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(fut);
// We only want to support native asyncio Futures.
// For further insight see the comment in the Python
// implementation of "future_add_to_awaited_by()".
assert(TaskOrFuture_Check(state, fut));
assert(TaskOrFuture_Check(state, thing));

/* Most futures/task are only awaited by one entity, so we want
to avoid always creating a set for `fut_awaited_by`.
*/
if (_fut->fut_awaited_by == NULL) {
assert(!_fut->fut_awaited_by_is_set);
if (fut->fut_awaited_by == NULL) {
assert(!fut->fut_awaited_by_is_set);
Py_INCREF(thing);
_fut->fut_awaited_by = thing;
fut->fut_awaited_by = thing;
return 0;
}

if (_fut->fut_awaited_by_is_set) {
assert(PySet_CheckExact(_fut->fut_awaited_by));
return PySet_Add(_fut->fut_awaited_by, thing);
if (fut->fut_awaited_by_is_set) {
assert(PySet_CheckExact(fut->fut_awaited_by));
return PySet_Add(fut->fut_awaited_by, thing);
}

PyObject *set = PySet_New(NULL);
Expand All @@ -583,40 +581,38 @@ future_awaited_by_add(asyncio_state *state, PyObject *fut, PyObject *thing)
Py_DECREF(set);
return -1;
}
if (PySet_Add(set, _fut->fut_awaited_by)) {
if (PySet_Add(set, fut->fut_awaited_by)) {
Py_DECREF(set);
return -1;
}
Py_SETREF(_fut->fut_awaited_by, set);
_fut->fut_awaited_by_is_set = 1;
Py_SETREF(fut->fut_awaited_by, set);
fut->fut_awaited_by_is_set = 1;
return 0;
}

static int
future_awaited_by_discard(asyncio_state *state, PyObject *fut, PyObject *thing)
future_awaited_by_discard(asyncio_state *state, FutureObj *fut, PyObject *thing)
{
if (!TaskOrFuture_Check(state, fut) || !TaskOrFuture_Check(state, thing)) {
// We only want to support native asyncio Futures.
// For further insight see the comment in the Python
// implementation of "future_add_to_awaited_by()".
return 0;
}

FutureObj *_fut = (FutureObj *)fut;
_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(fut);
// We only want to support native asyncio Futures.
// For further insight see the comment in the Python
// implementation of "future_add_to_awaited_by()".
assert(TaskOrFuture_Check(state, fut));
assert(TaskOrFuture_Check(state, thing));

/* Following the semantics of 'set.discard()' here in not
raising an error if `thing` isn't in the `awaited_by` "set".
*/
if (_fut->fut_awaited_by == NULL) {
if (fut->fut_awaited_by == NULL) {
return 0;
}
if (_fut->fut_awaited_by == thing) {
Py_CLEAR(_fut->fut_awaited_by);
if (fut->fut_awaited_by == thing) {
Py_CLEAR(fut->fut_awaited_by);
return 0;
}
if (_fut->fut_awaited_by_is_set) {
assert(PySet_CheckExact(_fut->fut_awaited_by));
int err = PySet_Discard(_fut->fut_awaited_by, thing);
if (fut->fut_awaited_by_is_set) {
assert(PySet_CheckExact(fut->fut_awaited_by));
int err = PySet_Discard(fut->fut_awaited_by, thing);
if (err < 0) {
return -1;
} else {
Expand All @@ -626,36 +622,6 @@ future_awaited_by_discard(asyncio_state *state, PyObject *fut, PyObject *thing)
return 0;
}

/*[clinic input]
@critical_section
@getter
_asyncio.Future._asyncio_awaited_by
[clinic start generated code]*/

static PyObject *
_asyncio_Future__asyncio_awaited_by_get_impl(FutureObj *self)
/*[clinic end generated code: output=932af76d385d2e2a input=64c1783df2d44d2b]*/
{
/* Implementation of a Python getter. */
if (self->fut_awaited_by == NULL) {
Py_RETURN_NONE;
}
if (self->fut_awaited_by_is_set) {
/* Already a set, just wrap it into a frozen set and return. */
assert(PySet_CheckExact(self->fut_awaited_by));
return PyFrozenSet_New(self->fut_awaited_by);
}

PyObject *set = PyFrozenSet_New(NULL);
if (set == NULL) {
return NULL;
}
if (PySet_Add(set, self->fut_awaited_by)) {
Py_DECREF(set);
return NULL;
}
return set;
}

static PyObject *
future_set_result(asyncio_state *state, FutureObj *fut, PyObject *res)
Expand Down Expand Up @@ -1362,6 +1328,38 @@ _asyncio_Future_get_loop_impl(FutureObj *self, PyTypeObject *cls)
return Py_NewRef(self->fut_loop);
}

/*[clinic input]
@critical_section
@getter
_asyncio.Future._asyncio_awaited_by
[clinic start generated code]*/

static PyObject *
_asyncio_Future__asyncio_awaited_by_get_impl(FutureObj *self)
/*[clinic end generated code: output=932af76d385d2e2a input=64c1783df2d44d2b]*/
{
/* Implementation of a Python getter. */
if (self->fut_awaited_by == NULL) {
Py_RETURN_NONE;
}
if (self->fut_awaited_by_is_set) {
/* Already a set, just wrap it into a frozen set and return. */
assert(PySet_CheckExact(self->fut_awaited_by));
return PyFrozenSet_New(self->fut_awaited_by);
}

PyObject *set = PyFrozenSet_New(NULL);
if (set == NULL) {
return NULL;
}
if (PySet_Add(set, self->fut_awaited_by)) {
Py_DECREF(set);
return NULL;
}
return set;
}


/*[clinic input]
@critical_section
@getter
Expand Down Expand Up @@ -3298,8 +3296,11 @@ task_step_handle_result_impl(asyncio_state *state, TaskObj *task, PyObject *resu
if (!fut->fut_blocking) {
goto yield_insteadof_yf;
}

if (future_awaited_by_add(state, result, (PyObject *)task)) {
int res;
Py_BEGIN_CRITICAL_SECTION(result);
res = future_awaited_by_add(state, (FutureObj *)result, (PyObject *)task);
Py_END_CRITICAL_SECTION();
if (res) {
goto fail;
}

Expand Down Expand Up @@ -3392,8 +3393,14 @@ task_step_handle_result_impl(asyncio_state *state, TaskObj *task, PyObject *resu
goto yield_insteadof_yf;
}

if (future_awaited_by_add(state, result, (PyObject *)task)) {
goto fail;
if (TaskOrFuture_Check(state, result)) {
int res;
Py_BEGIN_CRITICAL_SECTION(result);
res = future_awaited_by_add(state, (FutureObj *)result, (PyObject *)task);
Py_END_CRITICAL_SECTION();
if (res) {
goto fail;
}
}

/* result._asyncio_future_blocking = False */
Expand Down Expand Up @@ -3608,8 +3615,14 @@ task_wakeup_lock_held(TaskObj *task, PyObject *o)

asyncio_state *state = get_asyncio_state_by_def((PyObject *)task);

if (future_awaited_by_discard(state, o, (PyObject *)task)) {
return NULL;
if (TaskOrFuture_Check(state, o)) {
int res;
Py_BEGIN_CRITICAL_SECTION(o);
res = future_awaited_by_discard(state, (FutureObj *)o, (PyObject *)task);
Py_END_CRITICAL_SECTION();
if (res) {
return NULL;
}
}

if (Future_CheckExact(state, o) || Task_CheckExact(state, o)) {
Expand Down Expand Up @@ -4112,8 +4125,14 @@ _asyncio_future_add_to_awaited_by_impl(PyObject *module, PyObject *fut,
/*[clinic end generated code: output=0ab9a1a63389e4df input=06e6eaac51f532b9]*/
{
asyncio_state *state = get_asyncio_state(module);
if (future_awaited_by_add(state, fut, waiter)) {
return NULL;
if (TaskOrFuture_Check(state, fut) && TaskOrFuture_Check(state, waiter)) {
int res;
Py_BEGIN_CRITICAL_SECTION(fut);
res = future_awaited_by_add(state, (FutureObj *)fut, waiter);
Py_END_CRITICAL_SECTION();
if (res) {
return NULL;
}
}
Py_RETURN_NONE;
}
Expand All @@ -4133,8 +4152,14 @@ _asyncio_future_discard_from_awaited_by_impl(PyObject *module, PyObject *fut,
/*[clinic end generated code: output=a03b0b4323b779de input=3833f7639e88e483]*/
{
asyncio_state *state = get_asyncio_state(module);
if (future_awaited_by_discard(state, fut, waiter)) {
return NULL;
if (TaskOrFuture_Check(state, fut) && TaskOrFuture_Check(state, waiter)) {
int res;
Py_BEGIN_CRITICAL_SECTION(fut);
res = future_awaited_by_add(state, (FutureObj *)fut, waiter);
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Sorry, this should have been future_awaited_by_discard, fixing #129731.

I'm surprised that no tests failed, seems like test coverage is less for these functions...

Py_END_CRITICAL_SECTION();
if (res) {
return NULL;
}
}
Py_RETURN_NONE;
}
Expand Down
52 changes: 26 additions & 26 deletions Modules/clinic/_asynciomodule.c.h
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