I want to implement my own version of _PyThread_CurrentFrames() https://github.com/python/cpython/blob/e838a9324c1719bb917ca81ede8d766b5cb55..., but it seems like it's not possible using public C-API. The comment https://github.com/python/cpython/blob/e838a9324c1719bb917ca81ede8d766b5cb55... in the source code of _PyThread_CurrentFrames() says that lists of interpreters and threads can be mutated even when GIL is held and so HEAD_LOCK() should be used. At the same time Advanced Debugger Support https://docs.python.org/3/c-api/init.html#advanced-debugger-support API exposes access to these lists but there is no way (or I don't see how) to achieve the same thing that HEAD_LOCK() does. Am I missing something or Advanced Debugger Support is incomplete? -- With kind regards, Andrew Pashkin. cell phone - +375 (44) 492-16-85 Skype - waves_in_fluids e-mail - andrew.pashkin@gmx.co.uk