Pablo Galindo Salgado <[email protected]> added the comment:
I am mentoring @BTaskaya and I asked to take a look a this. After some
debugging, we found that the problem is the following:
When the pull is not used via the context manager or terminate() is called,
there is a system in multiprocessing.util that handles finalization of all
pools via an atexit handler (the Finalize) class. This class registers the
_terminate_pool handler in the registry of finalizers of the module, and that
registry is called on interpreter exit via _exit_function.
The problem is that the "happy" path with the context manager or manual call to
finalize() does some extra steps that _terminate_pool does not:
def terminate(self):
util.debug('terminating pool')
self._state = TERMINATE
self._worker_handler._state = TERMINATE
self._change_notifier.put(None)
self._terminate()
In this code self._terminate() calls _terminate_pool. The step that is not
executed when the atexit() handler calls _terminate_pool is pinging the
_change_notifier queue to unblock the maintenance threads.
The fix is moving the "self._change_notifier.put(None)" to the _terminate_pool
function.
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Python tracker <[email protected]>
<https://bugs.python.org/issue38744>
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