Fix #651 and fix #652 by removing a runtime import.

.pep8

 [pep8]
 ignore=E702,E265,E402,E731,E266,E261,W503,E129
 max_line_length=160
-exclude=.eggs,.tox,.git,build,2.6,2.7,2.7pypy,3.3,test_support.py,test_queue.py,patched_tests_setup.py,test_threading_2.py,lock_tests.py,_sslgte279.py,3.4
+exclude=.eggs,.tox,.git,build,2.6,2.7,2.7pypy,3.3,3.5,test_support.py,test_queue.py,patched_tests_setup.py,test_threading_2.py,lock_tests.py,_sslgte279.py,3.4

changelog.rst

@@ -36,6 +36,13 @@
   ``subprocess.run`` but impacts all versions (``timeout`` is an
   official argument under Python 3 and a gevent extension with
   slightly different semantics under Python 2).
+- gevent blocking operations performed at the top-level of a module
+  after the system was monkey-patched under Python 2 could result in
+  raising a ``LoopExit`` instead of completing the expected blocking
+  operation. Note that performing gevent blocking operations in the
+  top-level of a module is typically not recommended, but this
+  situation can arise when monkey-patching existing scripts. Reported
+  in :issue:`651` and :issue:`652` by Mike Kaplinskiy.
 
 .. _WSGI specification: https://www.python.org/dev/peps/pep-3333/#the-start-response-callable
 

gevent/hub.py

@@ -820,19 +820,16 @@ class _MultipleWaiter(Waiter):
 
     This does not handle exceptions or throw methods.
     """
-    _DEQUE = None
     __slots__ = ['_values']
 
     def __init__(self, *args, **kwargs):
         Waiter.__init__(self, *args, **kwargs)
-        self._values = self._deque()
-
-    @classmethod
-    def _deque(cls):
-        if cls._DEQUE is None:
-            from collections import deque
-            cls._DEQUE = deque
-        return cls._DEQUE()
+        # we typically expect a relatively small number of these to be outstanding.
+        # since we pop from the left, a deque might be slightly
+        # more efficient, but since we're in the hub we avoid imports if
+        # we can help it to better support monkey-patching, and delaying the import
+        # here can be impractical (see https://github.com/gevent/gevent/issues/652)
+        self._values = list()
 
     def switch(self, value):
         self._values.append(value)
@@ -843,7 +840,7 @@ class _MultipleWaiter(Waiter):
             Waiter.get(self)
             Waiter.clear(self)
 
-        return self._values.popleft()
+        return self._values.pop(0)
 
 
 def iwait(objects, timeout=None, count=None):

greentest/_import_wait.py

+# test__import_wait.py calls this
+import gevent
+
+
+def fn2():
+    return 2
+
+
+def fn():
+    return gevent.wait([gevent.spawn(fn2), gevent.spawn(fn2)])
+
+x = gevent.spawn(fn).get()

greentest/test__import_wait.py

+# https://github.com/gevent/gevent/issues/652
+from gevent import monkey
+monkey.patch_all()
+
+import _import_wait
+
+assert _import_wait.x