Use an event variable to tell the notify queue to drain

Intended to speed up the notify queue shut down if there are pending
events when running tests that repeatedly create and destroy llfuse
sessions.

src/fuse_api.pxi

@@ -301,9 +301,11 @@ def main(workers=None, handle_signals=True):
  on_exit.callback(lambda: restore_signal_handlers())
 
  # Start notification handling thread
+ _notify_queue_shutdown.clear()
  t = threading.Thread(target=_notify_loop)
  t.daemon = True
  t.start()
+ on_exit.callback(_notify_queue_shutdown.set)
  on_exit.callback(_notify_queue.put, None, block=True, timeout=5)
 
  on_exit.callback(lambda: fuse_session_reset(session))

src/llfuse.pyx

@@ -137,6 +137,9 @@ lock_released = NoLockManager.__new__(NoLockManager)
 cdef object _notify_queue
 _notify_queue = Queue(maxsize=1000)
 
+cdef object _notify_queue_shutdown
+_notify_queue_shutdown = threading.Event()
+
 # Exported for access from Python code
 # (in the Cython source, we want ENOATTR to refer
 # to the C constant, not a Python object)

src/misc.pxi

@@ -267,7 +267,11 @@ def _notify_loop():
  while True:
  req = _notify_queue.get()
  if req is None:
- return
+ break
+
+ if _notify_queue_shutdown.is_set():
+ # Just drain the queue
+ continue
 
  if req.kind == NOTIFY_INVAL_INODE:
  if req.attr_only: