events: Make trace events happen at the right priority.

Also, while we're at it, remember that priorities are in the Event class
and add a disable method to disable tracing.

src/python/m5/event.py

@@ -35,13 +35,16 @@ mainq = internal.event.cvar.mainEventQueue
 
 def create(obj, priority=None):
     if priority is None:
-        priority = internal.event.Event.Default_Pri
+        priority = Event.Default_Pri
     return PythonEvent(obj, priority)
 
+
+# As a reminder, priorities found in sim/eventq.hh are stuck into the
+# Event class by swig
 class Event(PythonEvent):
     def __init__(self, priority=None):
         if priority is None:
-            priority = internal.event.Event.Default_Pri
+            priority = Event.Default_Pri
         super(Event, self).__init__(self, priority)
 
 class ProgressEvent(Event):

src/python/m5/main.py

@@ -312,7 +312,7 @@ def main():
 
     if options.trace_start:
         check_tracing()
-        e = event.create(trace.enable)
+        e = event.create(trace.enable, Event.Trace_Enable_Pri)
         event.mainq.schedule(e, options.trace_start)
     else:
         trace.enable()

src/python/m5/trace.py

@@ -32,6 +32,9 @@ import util
 
 from internal.trace import clear, output, set, ignore
 
+def disable():
+    internal.trace.cvar.enabled = False
+
 def enable():
     internal.trace.cvar.enabled = True