We've seen tracebacks in production like:
File "<frozen importlib._bootstrap>", line 1004, in _find_and_load(name='oe.gpg_sign', import_=<built-in function __import__>)
File "<frozen importlib._bootstrap>", line 158, in _ModuleLockManager.__enter__()
File "<frozen importlib._bootstrap>", line 110, in _ModuleLock.acquire()
KeyError: 139622474778432
and
File "<frozen importlib._bootstrap>", line 1004, in _find_and_load(name='oe.path', import_=<built-in function __import__>)
File "<frozen importlib._bootstrap>", line 158, in _ModuleLockManager.__enter__()
File "<frozen importlib._bootstrap>", line 110, in _ModuleLock.acquire()
KeyError: 140438942700992
I've attached a reproduction script which shows that if an import XXX is in progress and waiting at the wrong point when an interrupt arrives (in this case a signal) and triggers it's own import YYY, _blocking_on[tid] in importlib/_bootstrap.py gets overwritten and lost, triggering the traceback we see above upon exit from the second import.
I'm using a signal handler here as the interrupt, I don't know what our production source is as yet but this reproducer proves it is possible.
This is a production backtrace after I inserted code to traceback if tid was already in _blocking_on. It is being triggered by a warning about an unclosed asyncio event loop and confirms my theory about nested imports, in the production case I'd guess being triggered by gc given the __del__.
File "/home/pokybuild/yocto-worker/oe-selftest-fedora/build/meta/classes/base.bbclass", line 26, in oe_import
import oe.data
File "<frozen importlib._bootstrap>", line 1024, in _find_and_load
File "<frozen importlib._bootstrap>", line 171, in __enter__
File "/home/pokybuild/yocto-worker/oe-selftest-fedora/build/bitbake/lib/bb/cooker.py", line 168, in acquire
return orig_acquire(self)
File "<frozen importlib._bootstrap>", line 110, in acquire
File "/usr/lib64/python3.10/asyncio/base_events.py", line 685, in __del__
_warn(f"unclosed event loop {self!r}", ResourceWarning, source=self)
File "/usr/lib64/python3.10/warnings.py", line 112, in _showwarnmsg
_showwarnmsg_impl(msg)
File "/usr/lib64/python3.10/warnings.py", line 28, in _showwarnmsg_impl
text = _formatwarnmsg(msg)
File "/usr/lib64/python3.10/warnings.py", line 128, in _formatwarnmsg
return _formatwarnmsg_impl(msg)
File "/usr/lib64/python3.10/warnings.py", line 56, in _formatwarnmsg_impl
import tracemalloc
File "<frozen importlib._bootstrap>", line 1024, in _find_and_load
File "<frozen importlib._bootstrap>", line 171, in __enter__
File "/home/pokybuild/yocto-worker/oe-selftest-fedora/build/bitbake/lib/bb/cooker.py", line 167, in acquire
bb.warn("\n".join(traceback.format_stack()))