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Gregory P. Smith
9a57179d74
Make _find_and_load() acquire the module locks for the full dotted-name chain (parent before child) when loading a nested module, so both threads contend on the same first lock and serialise instead of deadlocking. When acquiring a parent's lock would itself deadlock with another thread that is loading that parent (cross-package circular imports), the parent's lock is skipped and the partially-initialised parent is accepted -- the same policy _lock_unlock_module() already applies on the existing code path -- so concurrent circular imports that worked before continue to work.