Greenlet can cimport waiter.

src/gevent/_greenlet.pxd

@@ -3,10 +3,12 @@
 cimport cython
 from gevent.__ident cimport IdentRegistry
 from gevent.__hub_local cimport get_hub_noargs as get_hub
-cdef bint _greenlet_imported
+from gevent.__waiter cimport Waiter
+
 cdef bint _PYPY
 cdef sys_getframe
 cdef sys_exc_info
+cdef Timeout
 
 cdef extern from "greenlet/greenlet.h":
 
@@ -19,9 +21,12 @@ cdef extern from "greenlet/greenlet.h":
     greenlet PyGreenlet_GetCurrent()
     void PyGreenlet_Import()
 
+@cython.final
 cdef inline greenlet getcurrent():
     return PyGreenlet_GetCurrent()
 
+cdef bint _greenlet_imported
+
 cdef inline void greenlet_init():
     global _greenlet_imported
     if not _greenlet_imported:

src/gevent/greenlet.py

@@ -17,7 +17,6 @@ from gevent._tblib import load_traceback
 
 from gevent.hub import GreenletExit
 from gevent.hub import InvalidSwitchError
-from gevent.hub import Waiter
 from gevent.hub import iwait
 from gevent.hub import wait
 
@@ -27,6 +26,8 @@ from gevent._config import config as GEVENT_CONFIG
 from gevent._util import Lazy
 from gevent._util import readproperty
 from gevent._hub_local import get_hub_noargs as get_hub
+from gevent import _waiter
+
 
 __all__ = [
     'Greenlet',
@@ -35,14 +36,13 @@ __all__ = [
 ]
 
 
-
 # In Cython, we define these as 'cdef inline' functions. The
 # compilation unit cannot have a direct assignment to them (import
 # is assignment) without generating a 'lvalue is not valid target'
 # error.
 locals()['getcurrent'] = __import__('greenlet').getcurrent
 locals()['greenlet_init'] = lambda: None
-
+locals()['Waiter'] = _waiter.Waiter
 
 
 if _PYPY:
@@ -638,7 +638,7 @@ class Greenlet(greenlet):
         if self.dead:
             self.__handle_death_before_start((exception,))
         else:
-            waiter = Waiter() if block else None
+            waiter = Waiter() if block else None # pylint:disable=undefined-variable
             self.parent.loop.run_callback(_kill, self, exception, waiter)
             if block:
                 waiter.get()
@@ -955,7 +955,7 @@ def killall(greenlets, exception=GreenletExit, block=True, timeout=None):
         return
     loop = greenlets[0].loop
     if block:
-        waiter = Waiter()
+        waiter = Waiter() # pylint:disable=undefined-variable
         loop.run_callback(_killall3, greenlets, exception, waiter)
         t = Timeout._start_new_or_dummy(timeout)
         try:

src/gevent/hub.py

@@ -162,7 +162,7 @@ def sleep(seconds=0, ref=True):
     hub = _get_hub_noargs()
     loop = hub.loop
     if seconds <= 0:
-        waiter = Waiter()
+        waiter = Waiter(hub)
         loop.run_callback(waiter.switch)
         waiter.get()
     else:
@@ -672,7 +672,7 @@ class Hub(TrackedRawGreenlet):
         if self.dead:
             return True
 
-        waiter = Waiter()
+        waiter = Waiter(self)
 
         if timeout is not None:
             timeout = self.loop.timer(timeout, ref=False)
@@ -782,16 +782,17 @@ def iwait(objects, timeout=None, count=None):
        in between items yielded by this function.
     """
     # QQQ would be nice to support iterable here that can be generated slowly (why?)
+    hub = _get_hub_noargs()
     if objects is None:
-        yield _get_hub_noargs().join(timeout=timeout)
+        yield hub.join(timeout=timeout)
         return
 
     count = len(objects) if count is None else min(count, len(objects))
-    waiter = _MultipleWaiter()
+    waiter = _MultipleWaiter(hub)
     switch = waiter.switch
 
     if timeout is not None:
-        timer = _get_hub_noargs().loop.timer(timeout, priority=-1)
+        timer = hub.loop.timer(timeout, priority=-1)
         timer.start(switch, _NONE)
 
     try: