[Python-apps-team] Bug#959097: Acknowledgement (vdirsyncer: hang in FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME for some configs)

[Bernhard Reiter]

Additional info:

Here is a backtrace showing the hang run via
the python3-click-threading package (Version: 0.4.4-1)

Another info: The hang also happens to me on the same calender setup
on a different Debian Buster machine.

apt-get install python3-dbg
allows
ps -u bernh | grep vdir
16249 pts/11   00:41:23 vdirsyncer
bernh at machine ~> gdb -p 16249
(gdb) py-bt
Traceback (most recent call first):
  File "/usr/lib/python3.7/threading.py", line 296, in wait
    waiter.acquire()
  File "/usr/lib/python3.7/queue.py", line 170, in get
    self.not_empty.wait()
  File "/usr/lib/python3/dist-packages/click_threading/__init__.py", line 110, in run
    func, future = self.tasks.get()
  File "/usr/lib/python3/dist-packages/vdirsyncer/cli/utils.py", line 375, in join
    ui_worker.run()
  <built-in method next of module object at remote 0x7f387d2bcc28>
  File "/usr/lib/python3.7/contextlib.py", line 119, in __exit__
    next(self.gen)
  File "/usr/lib/python3/dist-packages/vdirsyncer/cli/__init__.py", line 154, in sync
    wq.spawn_worker()
  File "/usr/lib/python3/dist-packages/vdirsyncer/cli/__init__.py", line 32, in inner
    f(*a, **kw)
  File "/usr/lib/python3/dist-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/decorators.py", line 64, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3/dist-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3/dist-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/usr/bin/vdirsyncer", line 11, in <module>
    load_entry_point('vdirsyncer==0.16.7', 'console_scripts', 'vdirsyncer')()