Detect OSError errno EBADF and re-raise as trio.BrokenResourceError on EventFD reads

tractor/linux/eventfd.py

@@ -163,11 +163,18 @@ class EventFD:
         async with self._read_lock:
             self._cscope = trio.CancelScope()
             with self._cscope:
+                try:
                     return await trio.to_thread.run_sync(
                         read_eventfd, self._fd,
                         abandon_on_cancel=True
                     )
 
+                except OSError as e:
+                    if e.errno != errno.EBADF:
+                        raise
+
+                    raise trio.BrokenResourceError
+
             if self._cscope.cancelled_caught:
                 raise EFDReadCancelled