eventq: Major API change for the Event and EventQueue structures.

Since the early days of M5, an event needed to know which event queue
it was on, and that data was required at the time of construction of
the event object.  In the future parallelized M5, this sort of
requirement does not work well since the proper event queue will not
always be known at the time of construction of an event.  Now, events
are created, and the EventQueue itself has the schedule function,
e.g. eventq->schedule(event, when).  To simplify the syntax, I created
a class called EventManager which holds a pointer to an EventQueue and
provides the schedule interface that is a proxy for the EventQueue.
The intent is that objects that frequently schedule events can be
derived from EventManager and then they have the schedule interface.
SimObject and Port are examples of objects that will become
EventManagers.  The end result is that any SimObject can just call
schedule(event, when) and it will just call that SimObject's
eventq->schedule function.  Of course, some objects may have more than
one EventQueue, so this interface might not be perfect for those, but
they should be relatively few.

11 files changed, 254 insertions, 219 deletions

diff --git a/src/mem/port.cc b/src/mem/port.cc
index 0e03194c9..a666c968b 100644
--- a/src/mem/port.cc
+++ b/src/mem/port.cc
@@ -49,7 +49,7 @@ class DefaultPeerPort : public Port
 
   public:
     DefaultPeerPort()
-        : Port("default_port")
+        : Port("default_port", NULL)
     { }
 
     bool recvTiming(PacketPtr)
@@ -90,13 +90,9 @@ class DefaultPeerPort : public Port
 
 DefaultPeerPort defaultPeerPort;
 
-Port::Port()
-    : peer(&defaultPeerPort), owner(NULL)
-{
-}
-
 Port::Port(const std::string &_name, MemObject *_owner)
-    : portName(_name), peer(&defaultPeerPort), owner(_owner)
+    : EventManager(_owner), portName(_name), peer(&defaultPeerPort),
+      owner(_owner)
 {
 }
 
@@ -113,6 +109,13 @@ Port::setPeer(Port *port)
 }
 
 void
+Port::setOwner(MemObject *_owner)
+{
+    eventq = _owner->queue();
+    owner = _owner;
+}
+
+void
 Port::removeConn()
 {
     if (peer->getOwner())
diff --git a/src/mem/port.hh b/src/mem/port.hh
index 15fda2164..1d9135ae6 100644
--- a/src/mem/port.hh
+++ b/src/mem/port.hh
@@ -47,6 +47,7 @@
 #include "base/range.hh"
 #include "mem/packet.hh"
 #include "mem/request.hh"
+#include "sim/eventq.hh"
 
 /** This typedef is used to clean up the parameter list of
  * getDeviceAddressRanges() and getPeerAddressRanges().  It's declared
@@ -58,6 +59,7 @@
 typedef std::list<Range<Addr> > AddrRangeList;
 typedef std::list<Range<Addr> >::iterator AddrRangeIter;
 
+class EventQueue;
 class MemObject;
 
 /**
@@ -71,7 +73,7 @@ class MemObject;
  * Send accessor functions are being called from the device the port is
  * associated with, and it will call the peer recv. accessor function.
  */
-class Port
+class Port : public EventManager
 {
   protected:
     /** Descriptive name (for DPRINTF output) */
@@ -86,9 +88,6 @@ class Port
     MemObject *owner;
 
   public:
-
-    Port();
-
     /**
      * Constructor.
      *
@@ -97,7 +96,7 @@ class Port
      * @param _owner Pointer to the MemObject that owns this port.
      * Will not necessarily be set.
      */
-    Port(const std::string &_name, MemObject *_owner = NULL);
+    Port(const std::string &_name, MemObject *_owner);
 
     /** Return port name (for DPRINTF). */
     const std::string &name() const { return portName; }
@@ -121,7 +120,7 @@ class Port
     Port *getPeer() { return peer; }
 
     /** Function to set the owner of this port. */
-    void setOwner(MemObject *_owner) { owner = _owner; }
+    void setOwner(MemObject *_owner);
 
     /** Function to return the owner of this port. */
     MemObject *getOwner() { return owner; }
diff --git a/src/python/m5/event.py b/src/python/m5/event.py
index 2d6497464..5d50448e7 100644
--- a/src/python/m5/event.py
+++ b/src/python/m5/event.py
@@ -26,17 +26,32 @@
 #
 # Authors: Nathan Binkert
 
-from internal.event import create
-from internal.event import SimLoopExitEvent as SimExit
+import internal.event
 
-class ProgressEvent(object):
-    def __init__(self, period):
-        self.period = int(period)
-        self.schedule()
+from internal.event import PythonEvent, SimLoopExitEvent as SimExit
+
+mainq = internal.event.cvar.mainEventQueue
+
+def create(obj, priority=None):
+    if priority is None:
+        priority = internal.event.Event.Default_Pri
+    return internal.event.PythonEvent(obj, priority)
 
-    def schedule(self):
-        create(self, m5.curTick() + self.period)
+class Event(PythonEvent):
+    def __init__(self, priority=None):
+        if priority is None:
+            priority = internal.event.Event.Default_Pri
+        super(PythonEvent, self).__init__(self, priority)
+
+class ProgressEvent(Event):
+    def __init__(self, eventq, period):
+        super(ProgressEvent, self).__init__()
+        self.period = int(period)
+        self.eventq = eventq
+        self.eventq.schedule(self, m5.curTick() + self.period)
 
     def __call__(self):
         print "Progress! Time now %fs" % (m5.curTick()/1e12)
-        self.schedule()
+        self.eventq.schedule(self, m5.curTick() + self.period)
+
+__all__ = [ 'create', 'Event', 'ProgressEvent', 'SimExit', 'mainq' ]
diff --git a/src/python/swig/event.i b/src/python/swig/event.i
index 9a2093c99..10d75d2de 100644
--- a/src/python/swig/event.i
+++ b/src/python/swig/event.i
@@ -32,34 +32,36 @@
 
 %{
 #include "python/swig/pyevent.hh"
-
+#include "sim/host.hh"
+#include "sim/eventq.hh"
 #include "sim/sim_events.hh"
 #include "sim/sim_exit.hh"
 #include "sim/simulate.hh"
 %}
 
+#pragma SWIG nowarn=350,351
+
+%import "base/fast_alloc.hh"
+%import "sim/serialize.hh"
+
 %include "stdint.i"
 %include "std_string.i"
 %include "sim/host.hh"
+%include "sim/eventq.hh"
+%include "python/swig/pyevent.hh"
 
-void create(PyObject *object, Tick when);
-
-class Event;
-class CountedDrainEvent : public Event {
-  public:
+struct CountedDrainEvent : public Event
+{
     void setCount(int _count);
 };
 
-CountedDrainEvent *createCountedDrain();
-void cleanupCountedDrain(Event *drain_event);
-
 // minimal definition of SimExitEvent interface to wrap
-class SimLoopExitEvent {
+class SimLoopExitEvent : public Event
+{
   public:
     std::string getCause();
     int getCode();
-    SimLoopExitEvent(EventQueue *q, Tick _when, Tick _repeat,
-                     const std::string &_cause, int c = 0);
+    SimLoopExitEvent(const std::string &_cause, int c, Tick _repeat = 0);
 };
 
 %exception simulate {
diff --git a/src/python/swig/pyevent.cc b/src/python/swig/pyevent.cc
index 7f23b8874..bf993bc3e 100644
--- a/src/python/swig/pyevent.cc
+++ b/src/python/swig/pyevent.cc
@@ -33,8 +33,8 @@
 #include "python/swig/pyevent.hh"
 #include "sim/async.hh"
 
-PythonEvent::PythonEvent(PyObject *obj, Tick when, Priority priority)
-    : Event(&mainEventQueue, priority), object(obj)
+PythonEvent::PythonEvent(PyObject *obj, Priority priority)
+    : Event(priority), object(obj)
 {
     if (object == NULL)
         panic("Passed in invalid object");
@@ -42,7 +42,6 @@ PythonEvent::PythonEvent(PyObject *obj, Tick when, Priority priority)
     Py_INCREF(object);
 
     setFlags(AutoDelete);
-    schedule(when);
 }
 
 PythonEvent::~PythonEvent()
@@ -67,3 +66,36 @@ PythonEvent::process()
         async_exception = true;
     }
 }
+
+Event *
+createCountedDrain()
+{
+    return new CountedDrainEvent();
+}
+
+void
+cleanupCountedDrain(Event *counted_drain)
+{
+    CountedDrainEvent *event =
+        dynamic_cast<CountedDrainEvent *>(counted_drain);
+    if (event == NULL) {
+        fatal("Called cleanupCountedDrain() on an event that was not "
+              "a CountedDrainEvent.");
+    }
+    assert(event->getCount() == 0);
+    delete event;
+}
+
+#if 0
+Event *
+create(PyObject *object, Event::Priority priority)
+{
+    return new PythonEvent(object, priority);
+}
+
+void
+destroy(Event *event)
+{
+    delete event;
+}
+#endif
diff --git a/src/python/swig/pyevent.hh b/src/python/swig/pyevent.hh
index 65e80e9e4..c6d6ac993 100644
--- a/src/python/swig/pyevent.hh
+++ b/src/python/swig/pyevent.hh
@@ -40,35 +40,13 @@ class PythonEvent : public Event
     PyObject *object;
 
   public:
-    PythonEvent(PyObject *obj, Tick when, Priority priority = Default_Pri);
+    PythonEvent(PyObject *obj, Event::Priority priority);
     ~PythonEvent();
 
     virtual void process();
 };
 
-inline void
-create(PyObject *object, Tick when)
-{
-    new PythonEvent(object, when);
-}
-
-inline Event *
-createCountedDrain()
-{
-    return new CountedDrainEvent();
-}
-
-inline void
-cleanupCountedDrain(Event *counted_drain)
-{
-    CountedDrainEvent *event =
-        dynamic_cast<CountedDrainEvent *>(counted_drain);
-    if (event == NULL) {
-        fatal("Called cleanupCountedDrain() on an event that was not "
-              "a CountedDrainEvent.");
-    }
-    assert(event->getCount() == 0);
-    delete event;
-}
+Event *createCountedDrain();
+void cleanupCountedDrain(Event *counted_drain);
 
 #endif // __PYTHON_SWIG_PYEVENT_HH__
diff --git a/src/sim/eventq.cc b/src/sim/eventq.cc
index 78d6a458f..f4fa0ac8b 100644
--- a/src/sim/eventq.cc
+++ b/src/sim/eventq.cc
@@ -51,7 +51,7 @@ using namespace std;
 // Events on this queue are processed at the *beginning* of each
 // cycle, before the pipeline simulation is performed.
 //
-EventQueue mainEventQueue("MainEventQueue");
+EventQueue mainEventQueue("Main Event Queue");
 
 #ifndef NDEBUG
 Counter Event::instanceCounter = 0;
@@ -209,8 +209,7 @@ Event::serialize(std::ostream &os)
 void
 Event::unserialize(Checkpoint *cp, const string &section)
 {
-    if (scheduled())
-        deschedule();
+    assert(!scheduled() && "we used to deschedule these events");
 
     UNSERIALIZE_SCALAR(_when);
     UNSERIALIZE_SCALAR(_priority);
@@ -224,7 +223,8 @@ Event::unserialize(Checkpoint *cp, const string &section)
 
     if (wasScheduled) {
         DPRINTF(Config, "rescheduling at %d\n", _when);
-        schedule(_when);
+        panic("need to figure out how to unserialize scheduled events");
+        //schedule(_when);
     }
 }
 
diff --git a/src/sim/eventq.hh b/src/sim/eventq.hh
index e0194a742..2db652b54 100644
--- a/src/sim/eventq.hh
+++ b/src/sim/eventq.hh
@@ -51,16 +51,6 @@
 
 class EventQueue;       // forward declaration
 
-//////////////////////
-//
-// Main Event Queue
-//
-// Events on this queue are processed at the *beginning* of each
-// cycle, before the pipeline simulation is performed.
-//
-// defined in eventq.cc
-//
-//////////////////////
 extern EventQueue mainEventQueue;
 
 /*
@@ -90,10 +80,6 @@ class Event : public Serializable, public FastAlloc
     static Event *insertBefore(Event *event, Event *curr);
     static Event *removeItem(Event *event, Event *last);
 
-    /// queue to which this event belongs (though it may or may not be
-    /// scheduled on this queue yet)
-    EventQueue *_queue;
-
     Tick _when;         //!< timestamp when event should be processed
     short _priority;    //!< event priority
     short _flags;
@@ -107,6 +93,10 @@ class Event : public Serializable, public FastAlloc
     /// more difficult.  Thus we use a global counter value when
     /// debugging.
     Counter instance;
+
+    /// queue to which this event belongs (though it may or may not be
+    /// scheduled on this queue yet)
+    EventQueue *queue;
 #endif
 
 #ifdef EVENTQ_DEBUG
@@ -114,11 +104,13 @@ class Event : public Serializable, public FastAlloc
     Tick whenScheduled; //!< time scheduled
 #endif
 
-  protected:
     void
-    setWhen(Tick when)
+    setWhen(Tick when, EventQueue *q)
     {
         _when = when;
+#ifndef NDEBUG
+        queue = q;
+#endif
 #ifdef EVENTQ_DEBUG
         whenScheduled = curTick;
 #endif
@@ -131,7 +123,8 @@ class Event : public Serializable, public FastAlloc
         Scheduled = 0x2,
         AutoDelete = 0x4,
         AutoSerialize = 0x8,
-        IsExitEvent = 0x10
+        IsExitEvent = 0x10,
+        IsMainQueue = 0x20
     };
 
     bool getFlags(Flags f) const { return (_flags & f) == f; }
@@ -139,8 +132,6 @@ class Event : public Serializable, public FastAlloc
     void clearFlags(Flags f) { _flags &= ~f; }
 
   protected:
-    EventQueue *queue() const { return _queue; }
-
     // This function isn't really useful if TRACING_ON is not defined
     virtual void trace(const char *action);     //!< trace event activity
 
@@ -205,11 +196,12 @@ class Event : public Serializable, public FastAlloc
      * Event constructor
      * @param queue that the event gets scheduled on
      */
-    Event(EventQueue *q, Priority p = Default_Pri)
-        : nextBin(NULL), nextInBin(NULL), _queue(q), _priority(p), _flags(None)
+    Event(Priority p = Default_Pri)
+        : nextBin(NULL), nextInBin(NULL), _priority(p), _flags(None)
     {
 #ifndef NDEBUG
         instance = ++instanceCounter;
+        queue = NULL;
 #endif
 #ifdef EVENTQ_DEBUG
         whenCreated = curTick;
@@ -256,16 +248,6 @@ class Event : public Serializable, public FastAlloc
     /// Determine if the current event is scheduled
     bool scheduled() const { return getFlags(Scheduled); }
 
-    /// Schedule the event with the current priority or default priority
-    void schedule(Tick t);
-
-    /// Reschedule the event with the current priority
-    // always parameter means to schedule if not already scheduled
-    void reschedule(Tick t, bool always = false);
-
-    /// Remove the event from the current schedule
-    void deschedule();
-
     /// Squash the current event
     void squash() { setFlags(Squashed); }
 
@@ -281,6 +263,7 @@ class Event : public Serializable, public FastAlloc
     /// Get the event priority
     int priority() const { return _priority; }
 
+#ifndef SWIG
     struct priority_compare
         : public std::binary_function<Event *, Event *, bool>
     {
@@ -293,55 +276,7 @@ class Event : public Serializable, public FastAlloc
 
     virtual void serialize(std::ostream &os);
     virtual void unserialize(Checkpoint *cp, const std::string &section);
-};
-
-template <class T, void (T::* F)()>
-void
-DelayFunction(Tick when, T *object)
-{
-    class DelayEvent : public Event
-    {
-      private:
-        T *object;
-
-      public:
-        DelayEvent(Tick when, T *o)
-            : Event(&mainEventQueue), object(o)
-            { setFlags(this->AutoDestroy); schedule(when); }
-        void process() { (object->*F)(); }
-        const char *description() const { return "delay"; }
-    };
-
-    new DelayEvent(when, object);
-}
-
-template <class T, void (T::* F)()>
-class EventWrapper : public Event
-{
-  private:
-    T *object;
-
-  public:
-    EventWrapper(T *obj, bool del = false,
-                 EventQueue *q = &mainEventQueue,
-                 Priority p = Default_Pri)
-        : Event(q, p), object(obj)
-    {
-        if (del)
-            setFlags(AutoDelete);
-    }
-
-    EventWrapper(T *obj, Tick t, bool del = false,
-                 EventQueue *q = &mainEventQueue,
-                 Priority p = Default_Pri)
-        : Event(q, p), object(obj)
-    {
-        if (del)
-            setFlags(AutoDelete);
-        schedule(t);
-    }
-
-    void process() { (object->*F)(); }
+#endif
 };
 
 /*
@@ -349,18 +284,14 @@ class EventWrapper : public Event
  */
 class EventQueue : public Serializable
 {
-  protected:
-    std::string objName;
-
   private:
+    std::string objName;
     Event *head;
 
     void insert(Event *event);
     void remove(Event *event);
 
   public:
-
-    // constructor
     EventQueue(const std::string &n)
         : objName(n), head(NULL)
     {}
@@ -370,7 +301,7 @@ class EventQueue : public Serializable
     // schedule the given event on this queue
     void schedule(Event *ev, Tick when);
     void deschedule(Event *ev);
-    void reschedule(Event *ev, Tick when);
+    void reschedule(Event *ev, Tick when, bool always = false);
 
     Tick nextTick() const { return head->when(); }
     Event *serviceOne();
@@ -406,83 +337,103 @@ class EventQueue : public Serializable
 
     bool debugVerify() const;
 
+#ifndef SWIG
     virtual void serialize(std::ostream &os);
     virtual void unserialize(Checkpoint *cp, const std::string &section);
+#endif
 };
 
+#ifndef SWIG
+class EventManager
+{
+  protected:
+    /** A pointer to this object's event queue */
+    EventQueue *eventq;
 
-//////////////////////
-//
-// inline functions
-//
-// can't put these inside declaration due to circular dependence
-// between Event and EventQueue classes.
-//
-//////////////////////
+  public:
+    EventManager(EventManager &em) : eventq(em.queue()) {}
+    EventManager(EventManager *em) : eventq(em ? em->queue() : NULL) {}
+    EventManager(EventQueue *eq) : eventq(eq) {}
 
-// schedule at specified time (place on event queue specified via
-// constructor)
-inline void
-Event::schedule(Tick when)
-{
-    _queue->schedule(this, when);
-}
+    EventQueue *
+    queue() const
+    {
+        return eventq;
+    }
 
-inline void
-Event::deschedule()
-{
-    _queue->deschedule(this);
-}
+    void
+    schedule(Event &event, Tick when)
+    {
+        eventq->schedule(&event, when);
+    }
 
-inline void
-Event::reschedule(Tick when, bool always)
-{
-    if (scheduled()) {
-        _queue->reschedule(this, when);
-    } else {
-        assert(always);
-        _queue->schedule(this, when);
+    void
+    deschedule(Event &event)
+    {
+        eventq->deschedule(&event);
     }
-}
 
-inline bool
-operator<(const Event &l, const Event &r)
-{
-    return l.when() < r.when() ||
-        (l.when() == r.when() && l.priority() < r.priority());
-}
+    void
+    reschedule(Event &event, Tick when, bool always = false)
+    {
+        eventq->reschedule(&event, when, always);
+    }
 
-inline bool
-operator>(const Event &l, const Event &r)
-{
-    return l.when() > r.when() ||
-        (l.when() == r.when() && l.priority() > r.priority());
-}
+    void
+    schedule(Event *event, Tick when)
+    {
+        eventq->schedule(event, when);
+    }
 
-inline bool
-operator<=(const Event &l, const Event &r)
-{
-    return l.when() < r.when() ||
-        (l.when() == r.when() && l.priority() <= r.priority());
-}
-inline bool
-operator>=(const Event &l, const Event &r)
-{
-    return l.when() > r.when() ||
-        (l.when() == r.when() && l.priority() >= r.priority());
-}
+    void
+    deschedule(Event *event)
+    {
+        eventq->deschedule(event);
+    }
 
-inline bool
-operator==(const Event &l, const Event &r)
+    void
+    reschedule(Event *event, Tick when, bool always = false)
+    {
+        eventq->reschedule(event, when, always);
+    }
+};
+
+template <class T, void (T::* F)()>
+void
+DelayFunction(EventQueue *eventq, Tick when, T *object)
 {
-    return l.when() == r.when() && l.priority() == r.priority();
+    class DelayEvent : public Event
+    {
+      private:
+        T *object;
+
+      public:
+        DelayEvent(T *o)
+            : object(o)
+        { setFlags(this->AutoDestroy); }
+        void process() { (object->*F)(); }
+        const char *description() const { return "delay"; }
+    };
+
+    eventq->schedule(new DelayEvent(object), when);
 }
 
-inline bool
-operator!=(const Event &l, const Event &r)
+template <class T, void (T::* F)()>
+class EventWrapper : public Event
 {
-    return l.when() != r.when() || l.priority() != r.priority();
-}
+  private:
+    T *object;
+
+  public:
+    EventWrapper(T *obj, bool del = false, Priority p = Default_Pri)
+        : Event(p), object(obj)
+    {
+        if (del)
+            setFlags(AutoDelete);
+    }
+
+    void process() { (object->*F)(); }
+};
 
 inline void
 EventQueue::schedule(Event *event, Tick when)
@@ -490,9 +441,13 @@ EventQueue::schedule(Event *event, Tick when)
     assert(when >= curTick);
     assert(!event->scheduled());
 
-    event->setWhen(when);
+    event->setWhen(when, this);
     insert(event);
     event->setFlags(Event::Scheduled);
+    if (this == &mainEventQueue)
+        event->setFlags(Event::IsMainQueue);
+    else
+        event->clearFlags(Event::IsMainQueue);
 
     if (DTRACE(Event))
         event->trace("scheduled");
@@ -516,18 +471,65 @@ EventQueue::deschedule(Event *event)
 }
 
 inline void
-EventQueue::reschedule(Event *event, Tick when)
+EventQueue::reschedule(Event *event, Tick when, bool always)
 {
     assert(when >= curTick);
-    assert(event->scheduled());
+    assert(always || event->scheduled());
 
-    remove(event);
-    event->setWhen(when);
+    if (event->scheduled())
+        remove(event);
+            
+    event->setWhen(when, this);
     insert(event);
     event->clearFlags(Event::Squashed);
+    event->setFlags(Event::Scheduled);
+    if (this == &mainEventQueue)
+        event->setFlags(Event::IsMainQueue);
+    else
+        event->clearFlags(Event::IsMainQueue);
 
     if (DTRACE(Event))
         event->trace("rescheduled");
 }
 
+inline bool
+operator<(const Event &l, const Event &r)
+{
+    return l.when() < r.when() ||
+        (l.when() == r.when() && l.priority() < r.priority());
+}
+
+inline bool
+operator>(const Event &l, const Event &r)
+{
+    return l.when() > r.when() ||
+        (l.when() == r.when() && l.priority() > r.priority());
+}
+
+inline bool
+operator<=(const Event &l, const Event &r)
+{
+    return l.when() < r.when() ||
+        (l.when() == r.when() && l.priority() <= r.priority());
+}
+inline bool
+operator>=(const Event &l, const Event &r)
+{
+    return l.when() > r.when() ||
+        (l.when() == r.when() && l.priority() >= r.priority());
+}
+
+inline bool
+operator==(const Event &l, const Event &r)
+{
+    return l.when() == r.when() && l.priority() == r.priority();
+}
+
+inline bool
+operator!=(const Event &l, const Event &r)
+{
+    return l.when() != r.when() || l.priority() != r.priority();
+}
+#endif
+
 #endif // __SIM_EVENTQ_HH__
diff --git a/src/sim/sim_object.cc b/src/sim/sim_object.cc
index 2c2213987..dad8f6e8b 100644
--- a/src/sim/sim_object.cc
+++ b/src/sim/sim_object.cc
@@ -59,7 +59,7 @@ SimObject::SimObjectList SimObject::simObjectList;
 // SimObject constructor: used to maintain static simObjectList
 //
 SimObject::SimObject(const Params *p)
-    : _params(p)
+    : EventManager(p->eventq), _params(p)
 {
 #ifdef DEBUG
     doDebugBreak = false;
diff --git a/src/sim/sim_object.hh b/src/sim/sim_object.hh
index 0141c16cc..d6d08f255 100644
--- a/src/sim/sim_object.hh
+++ b/src/sim/sim_object.hh
@@ -43,6 +43,7 @@
 #include <vector>
 
 #include "params/SimObject.hh"
+#include "sim/eventq.hh"
 #include "sim/serialize.hh"
 #include "sim/startup.hh"
 
@@ -54,7 +55,8 @@ class Event;
  * correspond to physical components and can be specified via the
  * config file (CPUs, caches, etc.).
  */
-class SimObject : public Serializable, protected StartupCallback
+class SimObject
+    : public EventManager, public Serializable, protected StartupCallback
 {
   public:
     enum State {
diff --git a/src/sim/sim_object_params.hh b/src/sim/sim_object_params.hh
index 5a629a949..74d433495 100644
--- a/src/sim/sim_object_params.hh
+++ b/src/sim/sim_object_params.hh
@@ -38,12 +38,14 @@ struct PyObject;
 
 #include <string>
 
+struct EventQueue;
 struct SimObjectParams
 {
     virtual ~SimObjectParams() {}
 
     std::string name;
     PyObject *pyobj;
+    EventQueue *eventq;
 };