Rework test__core_fork to run on Windows; however it shows that fork watchers aren't called there

changelog.rst

@@ -296,7 +296,7 @@
   Previously the child process would hang indefinitely. Reported in
   :issue:`230` by Lx Yu.
 - Fork watchers are more likely to (eventually) get called in a
-  multi-threaded program. See :issue:`154`.
+  multi-threaded program (except on Windows). See :issue:`154`.
 - ``gevent.killall`` accepts an arbitrary iterable for the greenlets
   to kill. Reported in :issue:`404` by Martin Bachwerk; seen in
   combination with older versions of simple-requests.

doc/whatsnew_1_1.rst

@@ -80,7 +80,8 @@ downstream libraries, notably `gunicorn`_.
   :func:`gevent.os.waitpid` (again monkey patched by default) and
   :func:`gevent.signal.signal` (which is monkey patched only for the
   :data:`signal.SIGCHLD` case). The latter two patches are new in 1.1.
-- Fork-watchers will be called, even in multi-threaded programs.
+- Fork-watchers will be called, even in multi-threaded programs
+  (except on Windows).
 - The default threadpool and threaded resolver work in child
   processes.
 - File descriptors are no longer leaked if

greentest/test__core_fork.py

@@ -2,6 +2,7 @@ from __future__ import print_function
 import gevent.monkey; gevent.monkey.patch_all()
 import gevent
 import os
+import multiprocessing
 
 hub = gevent.get_hub()
 pid = os.getpid()
@@ -15,10 +16,8 @@ def on_fork():
 fork_watcher = hub.loop.fork(ref=False)
 fork_watcher.start(on_fork)
 
-# fork watchers weren't firing in multi-threading processes.
-
 
-def run():
+def run(q):
     # libev only calls fork callbacks at the beginning of
     # the loop; we use callbacks extensively so it takes *two*
     # calls to sleep (with a timer) to actually get wrapped
@@ -28,15 +27,25 @@ def run():
     q.put(newpid)
 
 
-import multiprocessing
-# Use a thread to make us multi-threaded
-hub.threadpool.apply(lambda: None)
-
-q = multiprocessing.Queue()
-p = multiprocessing.Process(target=run)
-p.start()
-p_val = q.get()
-p.join()
-
-assert p_val is not None
-assert p_val != pid
+def test():
+    # Use a thread to make us multi-threaded
+    hub.threadpool.apply(lambda: None)
+    # If the Queue is global, q.get() hangs on Windows; must pass as
+    # an argument.
+    q = multiprocessing.Queue()
+    p = multiprocessing.Process(target=run, args=(q,))
+    p.start()
+    p.join()
+    p_val = q.get()
+
+    assert p_val is not None, "The fork watcher didn't run"
+    assert p_val != pid
+
+if __name__ == '__main__':
+    # Must call for Windows to fork properly; the fork can't be in the top-level
+    multiprocessing.freeze_support()
+    # fork watchers weren't firing in multi-threading processes.
+    # This test is designed to prove that they are.
+    # However, it fails on Windows: The fork watcher never runs!
+
+    test()

known_failures.py

@@ -56,6 +56,8 @@ if sys.platform == 'win32':
     # other Windows-related issues (need investigating)
     FAILING_TESTS += [
         'test__all__.py',
+        # fork watchers don't get called in multithreaded programs on windows
+        # No idea why.
         'test__core_fork.py',
         'test__issues461_471.py',
         'test__execmodules.py',