sim: simulate with multiple threads and event queues

This patch adds support for simulating with multiple threads, each of
which operates on an event queue.  Each sim object specifies which eventq
is would like to be on.  A custom barrier implementation is being added
using which eventqs synchronize.

The patch was tested in two different configurations:
1. ruby_network_test.py: in this simulation L1 cache controllers receive
   requests from the cpu. The requests are replied to immediately without
   any communication taking place with any other level.
2. twosys-tsunami-simple-atomic: this configuration simulates a client-server
   system which are connected by an ethernet link.

We still lack the ability to communicate using message buffers or ports. But
other things like simulation start and end, synchronizing after every quantum
are working.

Committed by: Nilay Vaish

src/python/m5/event.py

@@ -1,4 +1,6 @@
 # Copyright (c) 2006 The Regents of The University of Michigan
+# Copyright (c) 2013 Advanced Micro Devices, Inc.
+# Copyright (c) 2013 Mark D. Hill and David A. Wood
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -29,9 +31,9 @@
 import m5
 import internal.event
 
-from internal.event import PythonEvent, SimLoopExitEvent as SimExit
+from internal.event import PythonEvent, GlobalSimLoopExitEvent as SimExit
 
-mainq = internal.event.cvar.mainEventQueue
+mainq = None
 
 def create(obj, priority=None):
     if priority is None:
@@ -58,4 +60,10 @@ class ProgressEvent(Event):
         print "Progress! Time now %fs" % (m5.curTick()/1e12)
         self.eventq.schedule(self, m5.curTick() + self.period)
 
+def getEventQueue(index):
+    return internal.event.getEventQueue(index)
+
+def setEventQueue(eventq):
+    internal.event.curEventQueue(eventq)
+
 __all__ = [ 'create', 'Event', 'ProgressEvent', 'SimExit', 'mainq' ]