Index: Lib/test/test_os.py
===================================================================
--- Lib/test/test_os.py	(revision 85107)
+++ Lib/test/test_os.py	(working copy)
@@ -13,6 +13,7 @@
 import shutil
 from test import support
 import contextlib
+import mmap
 
 # Detect whether we're on a Linux system that uses the (now outdated
 # and unmaintained) linuxthreads threading library.  There's an issue
@@ -1029,13 +1030,18 @@
         self._kill(100)
 
     def _kill_with_event(self, event, name):
+        tagname = "python-test#test_os#%d" % os.getpid()
+        m = mmap.mmap(-1, 1, tagname)
+        m[0] = 0
         # Run a script which has console control handling enabled.
         proc = subprocess.Popen([sys.executable,
                    os.path.join(os.path.dirname(__file__),
-                                "win_console_handler.py")],
+                                "win_console_handler.py"), tagname],
                    creationflags=subprocess.CREATE_NEW_PROCESS_GROUP)
         # Let the interpreter startup before we send signals. See #3137.
-        time.sleep(0.5)
+        while m[0] == 0:
+            self.assertIsNone(proc.poll(), "subprocess died unexpectedly")
+            time.sleep(0.5)
         os.kill(proc.pid, event)
         # proc.send_signal(event) could also be done here.
         # Allow time for the signal to be passed and the process to exit.
Index: Lib/test/win_console_handler.py
===================================================================
--- Lib/test/win_console_handler.py	(revision 85107)
+++ Lib/test/win_console_handler.py	(working copy)
@@ -11,9 +11,11 @@
 from ctypes import wintypes
 import signal
 import ctypes
+import mmap
+import sys
 
 # Function prototype for the handler function. Returns BOOL, takes a DWORD.
-HandlerRoutine = wintypes.WINFUNCTYPE(wintypes.BOOL, wintypes.DWORD)
+HandlerRoutine = ctypes.WINFUNCTYPE(wintypes.BOOL, wintypes.DWORD)
 
 def _ctrl_handler(sig):
     """Handle a sig event and return 0 to terminate the process"""
@@ -38,6 +40,10 @@
         print("Unable to add SetConsoleCtrlHandler")
         exit(-1)
 
+    # Awake main process
+    m = mmap.mmap(-1, 1, sys.argv[1])
+    m[0] = 1
+
     # Do nothing but wait for the signal
     while True:
         pass