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gh-131141: fix data race in instrumentation while registering callback #131142

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Merged
merged 4 commits into from
Mar 12, 2025
Merged

gh-131141: fix data race in instrumentation while registering callback #131142

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902468a
fix data race in instrumentation
kumaraditya303 Mar 12, 2025
2a50009
📜🤖 Added by blurb_it.
blurb-it[bot] Mar 12, 2025
e746dcf
use stop the world pause
kumaraditya303 Mar 12, 2025
92949c8
fix typo
kumaraditya303 Mar 12, 2025
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-03-12-11-19-46.gh-issue-131141.tQz594.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix data race in :data:`sys.monitoring` instrumentation while registering callback.
23 changes: 13 additions & 10 deletions Python/instrumentation.c
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Expand Up @@ -3006,13 +3006,6 @@ static PyObject *make_branch_handler(int tool_id, PyObject *handler, bool right)
return (PyObject *)callback;
}

/* Consumes a reference to obj */
static PyObject *exchange_callables(int tool_id, int event_id, PyObject *obj)
{
PyInterpreterState *is = _PyInterpreterState_GET();
return _Py_atomic_exchange_ptr(&is->monitoring_callables[tool_id][event_id], obj);
}

PyObject *
_PyMonitoring_RegisterCallback(int tool_id, int event_id, PyObject *obj)
{
Expand All @@ -3036,11 +3029,21 @@ _PyMonitoring_RegisterCallback(int tool_id, int event_id, PyObject *obj)
return NULL;
}
}
Py_XDECREF(exchange_callables(tool_id, PY_MONITORING_EVENT_BRANCH_RIGHT, right));
res = exchange_callables(tool_id, PY_MONITORING_EVENT_BRANCH_LEFT, left);
PyInterpreterState *interp = _PyInterpreterState_GET();
_PyEval_StopTheWorld(interp);
PyObject *old_right = interp->monitoring_callables[tool_id][PY_MONITORING_EVENT_BRANCH_RIGHT];
interp->monitoring_callables[tool_id][PY_MONITORING_EVENT_BRANCH_RIGHT] = right;
res = interp->monitoring_callables[tool_id][PY_MONITORING_EVENT_BRANCH_LEFT];
interp->monitoring_callables[tool_id][PY_MONITORING_EVENT_BRANCH_LEFT] = left;
_PyEval_StartTheWorld(interp);
Py_XDECREF(old_right);
}
else {
res = exchange_callables(tool_id, event_id, Py_XNewRef(obj));
PyInterpreterState *interp = _PyInterpreterState_GET();
_PyEval_StopTheWorld(interp);
res = interp->monitoring_callables[tool_id][event_id];
interp->monitoring_callables[tool_id][event_id] = Py_XNewRef(obj);
_PyEval_StartTheWorld(interp);
}
if (res != NULL && Py_TYPE(res) == &_PyLegacyBranchEventHandler_Type) {
_PyLegacyBranchEventHandler *wrapper = (_PyLegacyBranchEventHandler *)res;
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