[gem5-dev] changeset in gem5: sim: fix reference counting of PythonEvent

[Curtis Dunham via gem5-dev]

changeset a0dab21e422f in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=a0dab21e422f
description:
        sim: fix reference counting of PythonEvent

        When gem5 is a slave to another simulator and the Python is only used
        to initialize the configuration (and not perform actual simulation), a
        "debug start" (--debug-start) event will get freed during or immediately
        after the initial Python frame's execution rather than remaining in the
        event queue. This tricky patch fixes the GC issue causing this.

diffstat:

 src/python/swig/event.i    |  4 ++++
 src/python/swig/pyevent.cc |  8 ++++----
 src/python/swig/pyevent.hh |  5 +++--
 3 files changed, 11 insertions(+), 6 deletions(-)

diffs (56 lines):

diff -r 87f7b5a07584 -r a0dab21e422f src/python/swig/event.i
--- a/src/python/swig/event.i   Thu Jan 22 05:01:31 2015 -0500
+++ b/src/python/swig/event.i   Tue Dec 23 11:51:40 2014 -0600
@@ -71,6 +71,10 @@
     }
 }
 
+%typemap(out) PythonEvent* {
+   result->object = $result = SWIG_NewPointerObj(SWIG_as_voidptr(result), 
SWIGTYPE_p_PythonEvent, SWIG_POINTER_NEW);
+}
+
 %ignore EventQueue::schedule;
 %ignore EventQueue::deschedule;
 
diff -r 87f7b5a07584 -r a0dab21e422f src/python/swig/pyevent.cc
--- a/src/python/swig/pyevent.cc        Thu Jan 22 05:01:31 2015 -0500
+++ b/src/python/swig/pyevent.cc        Tue Dec 23 11:51:40 2014 -0600
@@ -34,10 +34,10 @@
 #include "sim/async.hh"
 #include "sim/eventq.hh"
 
-PythonEvent::PythonEvent(PyObject *obj, Priority priority)
-    : Event(priority), object(obj)
+PythonEvent::PythonEvent(PyObject *code, Priority priority)
+    : Event(priority), eventCode(code)
 {
-    if (object == NULL)
+    if (code == NULL)
         panic("Passed in invalid object");
 }
 
@@ -49,7 +49,7 @@
 PythonEvent::process()
 {
     PyObject *args = PyTuple_New(0);
-    PyObject *result = PyObject_Call(object, args, NULL);
+    PyObject *result = PyObject_Call(eventCode, args, NULL);
     Py_DECREF(args);
 
     if (result) {
diff -r 87f7b5a07584 -r a0dab21e422f src/python/swig/pyevent.hh
--- a/src/python/swig/pyevent.hh        Thu Jan 22 05:01:31 2015 -0500
+++ b/src/python/swig/pyevent.hh        Tue Dec 23 11:51:40 2014 -0600
@@ -37,9 +37,10 @@
 class PythonEvent : public Event
 {
   private:
-    PyObject *object;
+    PyObject *eventCode; // PyObject to call to perform event
+  public:
+    PyObject *object;    // PyObject wrapping this PythonEvent
 
-  public:
     PythonEvent(PyObject *obj, Event::Priority priority);
     ~PythonEvent();
 
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