Boost::Python callback triggered from Non-Python created threads

Consider  we have virtual/abstract C++ class that's fully implemented in Python. And for some sake of necessity we have a callback method (e.g. as some sort of event) that is being triggered from different thread on C++ side and is handled in Python .
In such case corresponding callback methods have to manage global interpreter lock state with PyGILState_STATE member variable.
So the resulting C++ callback class definition will look like below (notice that Python method calls are wrapped up with GIL state handling code).

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class SessionStatusListenerCallback : public SessionStatusListener { public: SessionStatusListenerCallback(PyObject *pyObject) : self(pyObject) {} SessionStatusListenerCallback(PyObject* pyObject, const SessionStatusListener& listener) : self(pyObject), SessionStatusListener(listener) {} void onSessionStatusChanged(O2GSessionStatus status) { // GIL state handler PyGILState_STATE gstate; gstate = PyGILState_Ensure(); // Python callback call_method<void>(self, "onSessionStatusChanged", status); // GIL handler release PyGILState_Release(gstate); } void onLoginFailed(const char* error) { // GIL state handler PyGILState_STATE gstate; gstate = PyGILState_Ensure(); // Python callback call_method<void>(self, "onLoginFailed", error); // GIL handler release PyGILState_Release(gstate); } private: PyObject* const self; };