[main] RuntimeError: set_wakeup_fd only works in main thread

[devos50]

Encountered during the tests on Linux (in particular, src.tribler-core.tribler_core.components.metadata_store.tests.test_metadata_store_component.test_metadata_store_component):

self = <_UnixSelectorEventLoop running=False closed=False debug=False>
sig = <Signals.SIGCHLD: 17>
callback = <bound method BaseChildWatcher._sig_chld of <asyncio.unix_events.SafeChildWatcher object at 0x7facd585bbe0>>
args = ()

    def add_signal_handler(self, sig, callback, *args):
        """Add a handler for a signal.  UNIX only.
    
        Raise ValueError if the signal number is invalid or uncatchable.
        Raise RuntimeError if there is a problem setting up the handler.
        """
        if (coroutines.iscoroutine(callback) or
                coroutines.iscoroutinefunction(callback)):
            raise TypeError("coroutines cannot be used "
                            "with add_signal_handler()")
        self._check_signal(sig)
        self._check_closed()
        try:
            # set_wakeup_fd() raises ValueError if this is not the
            # main thread.  By calling it early we ensure that an
            # event loop running in another thread cannot add a signal
            # handler.
>           signal.set_wakeup_fd(self._csock.fileno())
E           ValueError: set_wakeup_fd only works in main thread

/usr/lib/python3.8/asyncio/unix_events.py:95: ValueError

During handling of the above exception, another exception occurred:

pyfuncitem = <Function test_metadata_store_component>

    def pytest_pyfunc_call(pyfuncitem):  # type: ignore
        """
        Run coroutines in an event loop instead of a normal function call.
        """
        fast = pyfuncitem.config.getoption("--aiohttp-fast")
        if asyncio.iscoroutinefunction(pyfuncitem.function):
            existing_loop = pyfuncitem.funcargs.get('proactor_loop')\
                or pyfuncitem.funcargs.get('loop', None)
            with _runtime_warning_context():
>               with _passthrough_loop_context(existing_loop, fast=fast) as _loop:

/usr/local/lib/python3.8/dist-packages/aiohttp/pytest_plugin.py:167: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib/python3.8/contextlib.py:113: in __enter__
    return next(self.gen)
/usr/local/lib/python3.8/dist-packages/aiohttp/pytest_plugin.py:145: in _passthrough_loop_context
    loop = setup_test_loop()
/usr/local/lib/python3.8/dist-packages/aiohttp/test_utils.py:528: in setup_test_loop
    watcher.attach_loop(loop)
/usr/lib/python3.8/asyncio/unix_events.py:927: in attach_loop
    loop.add_signal_handler(signal.SIGCHLD, self._sig_chld)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <_UnixSelectorEventLoop running=False closed=False debug=False>
sig = <Signals.SIGCHLD: 17>
callback = <bound method BaseChildWatcher._sig_chld of <asyncio.unix_events.SafeChildWatcher object at 0x7facd585bbe0>>
args = ()

    def add_signal_handler(self, sig, callback, *args):
        """Add a handler for a signal.  UNIX only.
    
        Raise ValueError if the signal number is invalid or uncatchable.
        Raise RuntimeError if there is a problem setting up the handler.
        """
        if (coroutines.iscoroutine(callback) or
                coroutines.iscoroutinefunction(callback)):
            raise TypeError("coroutines cannot be used "
                            "with add_signal_handler()")
        self._check_signal(sig)
        self._check_closed()
        try:
            # set_wakeup_fd() raises ValueError if this is not the
            # main thread.  By calling it early we ensure that an
            # event loop running in another thread cannot add a signal
            # handler.
            signal.set_wakeup_fd(self._csock.fileno())
        except (ValueError, OSError) as exc:
>           raise RuntimeError(str(exc))
E           RuntimeError: set_wakeup_fd only works in main thread

/usr/lib/python3.8/asyncio/unix_events.py:97: RuntimeError

This was supposed to be fixed by #6354 but it seems that it requires a bit more attention.

[ichorid]

Well, we're still missing pytest.mark.asyncio decorators (or statements) on some tests...