Py_NewInterpreter(), is this a bug in the python core?

[Thomas Heller]

freesteel schrieb:
> /*
> Is this a bug in Py_NewInterpreter?
> 
> The function below "MyThread" is instantiated from a windows worker
> thread, but I don't
> think that is relevant.
> (I can try this on a linux box, but I would have to compile a python
> library with debugging
> enabled.)
> 
> The following code fragment throws an exception in a debug version of
> python:
> */
> 
> UINT MyThread(LPVOID lpParam)
> {
> 	{
> 		cs.Lock(); // this is a CCriticalSection lock
> 		if (!Py_IsInitialized())
> 		{
> 			Py_Initialize();
> 			PyEval_InitThreads();
> 
> 			// global pointer to the main PyThreadState object
> 			mainThreadState = PyThreadState_Get();
> 			PyEval_ReleaseLock();
> 		}
> 		cs.Unlock();
> 	}
> 
> 	ASSERT(Py_IsInitialized());
> 	ASSERT(PyEval_ThreadsInitialized());
> 	ASSERT(mainThreadState);
> 	threadnum++;
> 
> 	// get the global lock
> 	PyEval_AcquireLock();
>     PyGILState_STATE gstate;
>     gstate = PyGILState_Ensure(); // Is tis necessary?
> 
> 
> 	PyThreadState_Swap(mainThreadState);
> 	PyThreadState* nts = Py_NewInterpreter();
> 
> /*
> 
> The exception is thrown inside the above function call:
> This statement tries to swap the new threadstate 'tstate' with the
> current one
> 	save_tstate = PyThreadState_Swap(tstate);
> 
> Inside PyThreadState_Swap the code uses another way
> 'PyGILState_GetThisThreadState()' to find the current thread state and
> compares this with the newly set thread state.
> Naturally you would expect the two to be equal but that test fails:
> #if defined(Py_DEBUG) && defined(WITH_THREAD)
> 	if (new) {
> 		PyThreadState *check = PyGILState_GetThisThreadState();
> 		if (check && check != new)
> 			Py_FatalError("Invalid thread state for this thread");
> 	}
> #endif
> 
> The variable 'check' looks as if it is the 'previous' thread state, as
> if changing the thread state
> is not been done properly. Py_FatalError is called and that's the end.
> 
> Is there a mistake in my code, or is there something wrong in how
> Py_NewInterpreter is implemented?

As far as I know, the PyGILState_... functions are incompatible with multiple
Python interpreters.

Thomas