diff -r a5bbef4205e0 asyncio/base_events.py
--- a/asyncio/base_events.py	Thu Jan 30 13:07:06 2014 -0800
+++ b/asyncio/base_events.py	Fri Jan 31 09:45:31 2014 +0100
@@ -603,38 +603,48 @@ class BaseEventLoop(events.AbstractEvent
         schedules the resulting callbacks, and finally schedules
         'call_later' callbacks.
         """
-        # Remove delayed calls that were cancelled from head of queue.
-        while self._scheduled and self._scheduled[0]._cancelled:
-            heapq.heappop(self._scheduled)
+        while True:
+            # Remove delayed calls that were cancelled from head of queue.
+            while self._scheduled and self._scheduled[0]._cancelled:
+                heapq.heappop(self._scheduled)
 
-        timeout = None
-        if self._ready:
-            timeout = 0
-        elif self._scheduled:
-            # Compute the desired timeout.
-            when = self._scheduled[0]._when
-            deadline = max(0, when - self.time())
-            if timeout is None:
-                timeout = deadline
+            timeout = None
+            if self._ready:
+                timeout = 0
+            elif self._scheduled:
+                # Compute the desired timeout.
+                when = self._scheduled[0]._when
+                deadline = max(0, when - self.time())
+                if timeout is None:
+                    timeout = deadline
+                else:
+                    timeout = min(timeout, deadline)
+
+            # TODO: Instrumentation only in debug mode?
+            if logger.isEnabledFor(logging.INFO):
+                t0 = self.time()
+                event_list = self._selector.select(timeout)
+                t1 = self.time()
+                if t1-t0 >= 1:
+                    level = logging.INFO
+                else:
+                    level = logging.DEBUG
+                if timeout is not None:
+                    logger.log(level, 'poll %.3f took %.3f seconds',
+                               timeout, t1-t0)
+                else:
+                    logger.log(level, 'poll took %.3f seconds', t1-t0)
             else:
-                timeout = min(timeout, deadline)
+                event_list = self._selector.select(timeout)
+            if event_list or self._ready:
+                break
+            if self._scheduled:
+                now = self.time() + self._granularity
+                if self._scheduled[0]._when <= now:
+                    break
+            # selector was interrupted by a signal, or the granularity
+            # is wrong (too precise) and the selector took less than timeout
 
-        # TODO: Instrumentation only in debug mode?
-        if logger.isEnabledFor(logging.INFO):
-            t0 = self.time()
-            event_list = self._selector.select(timeout)
-            t1 = self.time()
-            if t1-t0 >= 1:
-                level = logging.INFO
-            else:
-                level = logging.DEBUG
-            if timeout is not None:
-                logger.log(level, 'poll %.3f took %.3f seconds',
-                           timeout, t1-t0)
-            else:
-                logger.log(level, 'poll took %.3f seconds', t1-t0)
-        else:
-            event_list = self._selector.select(timeout)
         self._process_events(event_list)
 
         # Handle 'later' callbacks that are ready.