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/SimObject.py

@@ -11,7 +11,8 @@
 # modified or unmodified, in source code or in binary form.
 #
 # Copyright (c) 2004-2006 The Regents of The University of Michigan
-# Copyright (c) 2010 Advanced Micro Devices, Inc.
+# Copyright (c) 2010-20013 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
@@ -528,8 +529,6 @@ struct PyObject;
 #endif
 
 #include <string>
-
-class EventQueue;
 ''')
         for param in params:
             param.cxx_predecls(code)
@@ -558,16 +557,11 @@ class EventQueue;
         code.indent()
         if cls == SimObject:
             code('''
-    SimObjectParams()
-    {
-        extern EventQueue mainEventQueue;
-        eventq = &mainEventQueue;
-    }
+    SimObjectParams() {}
     virtual ~SimObjectParams() {}
 
     std::string name;
     PyObject *pyobj;
-    EventQueue *eventq;
             ''')
         for param in params:
             param.cxx_decl(code)
@@ -582,6 +576,14 @@ class EventQueue;
         return code
 
 
+# This *temporary* definition is required to support calls from the
+# SimObject class definition to the MetaSimObject methods (in
+# particular _set_param, which gets called for parameters with default
+# values defined on the SimObject class itself).  It will get
+# overridden by the permanent definition (which requires that
+# SimObject be defined) lower in this file.
+def isSimObjectOrVector(value):
+    return False
 
 # The SimObject class is the root of the special hierarchy.  Most of
 # the code in this class deals with the configuration hierarchy itself
@@ -592,9 +594,10 @@ class SimObject(object):
     __metaclass__ = MetaSimObject
     type = 'SimObject'
     abstract = True
-    cxx_header = "sim/sim_object.hh"
 
+    cxx_header = "sim/sim_object.hh"
     cxx_bases = [ "Drainable", "Serializable" ]
+    eventq_index = Param.UInt32(Parent.eventq_index, "Event Queue Index")
 
     @classmethod
     def export_method_swig_predecls(cls, code):