diff -r 7e1bed443d77 asyncio/base_events.py
--- a/asyncio/base_events.py	Tue Feb 10 14:37:37 2015 +0100
+++ b/asyncio/base_events.py	Tue Feb 17 22:12:48 2015 +0100
@@ -189,6 +189,7 @@
         # Identifier of the thread running the event loop, or None if the
         # event loop is not running
         self._thread_id = None
+        self._pid = os.getpid()
         self._clock_resolution = time.get_clock_info('monotonic').resolution
         self._exception_handler = None
         self._debug = (not sys.flags.ignore_environment
@@ -203,6 +204,15 @@
                 % (self.__class__.__name__, self.is_running(),
                    self.is_closed(), self.get_debug()))
 
+    def _detect_fork(self):
+        pid = os.getpid()
+        if pid != self._pid:
+            self._pid = pid
+            self._at_fork()
+
+    def _at_fork(self):
+        pass
+
     def create_task(self, coro):
         """Schedule a coroutine object.
 
@@ -1112,6 +1122,9 @@
             when = self._scheduled[0]._when
             timeout = max(0, when - self.time())
 
+        # detect fork before using the selector
+        self._detect_fork()
+
         if self._debug and timeout != 0:
             t0 = self.time()
             event_list = self._selector.select(timeout)
diff -r 7e1bed443d77 asyncio/proactor_events.py
--- a/asyncio/proactor_events.py	Tue Feb 10 14:37:37 2015 +0100
+++ b/asyncio/proactor_events.py	Tue Feb 17 22:12:48 2015 +0100
@@ -489,6 +489,10 @@
             f.add_done_callback(self._loop_self_reading)
 
     def _write_to_self(self):
+        # The self-pipe must not be shared between two processes: at fork,
+        # create a new pipe to unshare it
+        self._detect_fork()
+
         self._csock.send(b'\0')
 
     def _start_serving(self, protocol_factory, sock,
diff -r 7e1bed443d77 asyncio/selector_events.py
--- a/asyncio/selector_events.py	Tue Feb 10 14:37:37 2015 +0100
+++ b/asyncio/selector_events.py	Tue Feb 17 22:12:48 2015 +0100
@@ -94,6 +94,8 @@
             raise RuntimeError("Cannot close a running event loop")
         if self.is_closed():
             return
+        # detect fork before using the self-pipe or the selector
+        self._detect_fork()
         self._close_self_pipe()
         super().close()
         if self._selector is not None:
@@ -135,6 +137,9 @@
                 break
 
     def _write_to_self(self):
+        # detect fork before using the self-pipe
+        self._detect_fork()
+
         # This may be called from a different thread, possibly after
         # _close_self_pipe() has been called or even while it is
         # running.  Guard for self._csock being None or closed.  When
@@ -230,6 +235,8 @@
         """Add a reader callback."""
         self._check_closed()
         handle = events.Handle(callback, args, self)
+        # detect fork before using the selector
+        self._detect_fork()
         try:
             key = self._selector.get_key(fd)
         except KeyError:
@@ -246,6 +253,8 @@
         """Remove a reader callback."""
         if self.is_closed():
             return False
+        # detect fork before using the selector
+        self._detect_fork()
         try:
             key = self._selector.get_key(fd)
         except KeyError:
@@ -268,6 +277,8 @@
         """Add a writer callback.."""
         self._check_closed()
         handle = events.Handle(callback, args, self)
+        # detect fork before using the selector
+        self._detect_fork()
         try:
             key = self._selector.get_key(fd)
         except KeyError:
@@ -284,6 +295,8 @@
         """Remove a writer callback."""
         if self.is_closed():
             return False
+        # detect fork before using the selector
+        self._detect_fork()
         try:
             key = self._selector.get_key(fd)
         except KeyError:
diff -r 7e1bed443d77 asyncio/unix_events.py
--- a/asyncio/unix_events.py	Tue Feb 10 14:37:37 2015 +0100
+++ b/asyncio/unix_events.py	Tue Feb 17 22:12:48 2015 +0100
@@ -48,6 +48,16 @@
         super().__init__(selector)
         self._signal_handlers = {}
 
+    def _at_fork(self):
+        super()._at_fork()
+        parent_selector = self._selector
+        self._selector = type(parent_selector)()
+        for key in parent_selector.get_map().values():
+            self._selector.register(key.fileobj, key.events, key.data)
+        parent_selector.close()
+        self._close_self_pipe()
+        self._make_self_pipe()
+
     def _socketpair(self):
         return socket.socketpair()