PyThreadState.on_delete is a callback used to notify Python when a thread completes. _thread._set_sentinel() function creates a lock which is released when the thread completes. It sets on_delete callback to the internal release_sentinel() function. This lock is known as Threading._tstate_lock in the threading module. The release_sentinel() function uses the Python C API. The problem is that on_delete is called late in the Python finalization, when the C API is no longer fully working. The PyThreadState_Clear() function now calls the PyThreadState.on_delete callback. Previously, that happened in PyThreadState_Delete(). The release_sentinel() function is now called when the C API is still fully working.
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PyThreadState.on_delete is a callback used to notify Python when a thread completes. _thread._set_sentinel() function creates a lock which is released when the thread completes. It sets on_delete callback to the internal release_sentinel() function. This lock is known as Threading._tstate_lock in the threading module. The release_sentinel() function uses the Python C API. The problem is that on_delete is called late in the Python finalization, when the C API is no longer fully working. The PyThreadState_Clear() function now calls the PyThreadState.on_delete callback. Previously, that happened in PyThreadState_Delete(). The release_sentinel() function is now called when the C API is still fully working.