diff -r 546cad3627e2 Lib/selectors.py
--- a/Lib/selectors.py	Thu Dec 05 22:47:19 2013 +0100
+++ b/Lib/selectors.py	Thu Dec 05 15:13:18 2013 -0800
@@ -89,6 +89,15 @@
 
         Returns:
         SelectorKey instance
+
+        Raises:
+        ValueError if events is invalid
+        KeyError if fileobj is already registered
+        OSError if fileobj is closed or otherwise is unacceptable to
+                the underlying system call (if a system call is made)
+
+        Note:
+        OSError may or may not be raised
         """
         raise NotImplementedError
 
@@ -101,6 +110,13 @@
 
         Returns:
         SelectorKey instance
+
+        Raises:
+        KeyError if fileobj is not registered
+
+        Note:
+        If fileobj is registered but has since been closed this does
+        *not* raise OSError (even if the wrapped syscall does)
         """
         raise NotImplementedError
 
@@ -114,6 +130,9 @@
 
         Returns:
         SelectorKey instance
+
+        Raises:
+        Anything that unregister() or register() raises
         """
         self.unregister(fileobj)
         return self.register(fileobj, events, data)
@@ -305,7 +324,10 @@
 
         def unregister(self, fileobj):
             key = super().unregister(fileobj)
-            self._poll.unregister(key.fd)
+            try:
+                self._poll.unregister(key.fd)
+            except OSError:
+                pass
             return key
 
         def select(self, timeout=None):
@@ -352,7 +374,10 @@
 
         def unregister(self, fileobj):
             key = super().unregister(fileobj)
-            self._epoll.unregister(key.fd)
+            try:
+                self._epoll.unregister(key.fd)
+            except OSError:
+                pass
             return key
 
         def select(self, timeout=None):
@@ -409,11 +434,17 @@
             if key.events & EVENT_READ:
                 kev = select.kevent(key.fd, select.KQ_FILTER_READ,
                                     select.KQ_EV_DELETE)
-                self._kqueue.control([kev], 0, 0)
+                try:
+                    self._kqueue.control([kev], 0, 0)
+                except OSError:
+                    pass
             if key.events & EVENT_WRITE:
                 kev = select.kevent(key.fd, select.KQ_FILTER_WRITE,
                                     select.KQ_EV_DELETE)
-                self._kqueue.control([kev], 0, 0)
+                try:
+                    self._kqueue.control([kev], 0, 0)
+                except OSError:
+                    pass
             return key
 
         def select(self, timeout=None):