fsm: support graceful osmo_fsm_inst_term() cascades

Add global flag osmo_fsm_term_safely() -- if set to true, enable the following
behavior:

Detect osmo_fsm_inst_term() occuring within osmo_fsm_inst_term():
- collect deallocations until the outermost osmo_fsm_inst_term() is done.
- call osmo_fsm_inst_free() *after* dispatching the parent event.

If a struct osmo_fsm_inst enters osmo_fsm_inst_term() while another is already
within osmo_fsm_inst_term(), do not directly deallocate it, but talloc-reparent
it to a separate talloc context, to be deallocated with the outermost FSM inst.

The effect is that all osmo_fsm_inst freed within an osmo_fsm_inst_term()
cascade will stay allocated until all osmo_fsm_inst_term() are complete and all
of them will be deallocated at the same time.

Mark the deferred deallocation state as __thread in an attempt to make cascaded
deallocation handling threadsafe.  Keep the enable/disable flag separate, so
that it is global and not per-thread.

The feature is showcased by fsm_dealloc_test.c: with this feature, all of those
wild deallocation scenarios succeed.

Make fsm_dealloc_test a normal regression test in testsuite.at.

Rationale:

It is difficult to gracefully handle deallocations of groups of FSM instances
that reference each other. As soon as one child dispatching a cleanup event
causes its parent to deallocate before fsm.c was ready for it, deallocation
will hit a use-after-free. Before this patch, by using parent_term events and
distinct "terminating" FSM states, parent/child FSMs can be taught to wait for
all children to deallocate before deallocating the parent. But as soon as a
non-child / non-parent FSM instance is involved, or actually any other
cleanup() action that triggers parent FSMs or parent talloc contexts to become
unused, it is near impossible to think of all possible deallocation events
ricocheting, and to avoid running into freeing FSM instances that were still in
the middle of osmo_fsm_inst_term(), or FSM instances to enter
osmo_fsm_inst_term() more than once. This patch makes deallocation of "all
possible" setups of complex cross referencing FSM instances easy to handle
correctly, without running into use-after-free or double free situations, and,
notably, without changing calling code.

Change-Id: I8eda67540a1cd444491beb7856b9fcd0a3143b18

2 files changed, 3283 insertions, 225 deletions

diff --git a/tests/fsm/fsm_dealloc_test.c b/tests/fsm/fsm_dealloc_test.c
index 5a493ad2..f8d2b1ee 100644
--- a/tests/fsm/fsm_dealloc_test.c
+++ b/tests/fsm/fsm_dealloc_test.c
@@ -346,26 +346,24 @@ static struct scene *scene_alloc()
 
 	LOGP(DLGLOBAL, LOGL_DEBUG, "%s()\n", __func__);
 
-	/*
 	s->o[root] = obj_alloc(s, NULL, "root");
-	*/
 
 	s->o[branch0] = obj_alloc(s, s->o[root], "_branch0");
 
 	s->o[twig0a] = obj_alloc(s, s->o[branch0], "__twig0a");
 
-	/*
 	s->o[twig0b] = obj_alloc(s, s->o[branch0], "__twig0b");
 
 	s->o[branch1] = obj_alloc(s, s->o[root], "_branch1");
 	s->o[twig1a] = obj_alloc(s, s->o[branch1], "__twig1a");
 	s->o[twig1b] = obj_alloc(s, s->o[branch1], "__twig1b");
-	*/
 
 	s->o[other] = obj_alloc(s, NULL, "other");
 
 	obj_set_other(s->o[branch0], s->o[other]);
 	obj_set_other(s->o[twig0a], s->o[other]);
+	obj_set_other(s->o[branch1], s->o[other]);
+	obj_set_other(s->o[twig1a], s->o[root]);
 
 	return s;
 }
@@ -455,6 +453,7 @@ int main(void)
 
 	log_set_category_filter(osmo_stderr_target, DLGLOBAL, 1, LOGL_DEBUG);
 
+	osmo_fsm_term_safely(true);
 	osmo_fsm_register(&test_fsm);
 
 	ctx_blocks = talloc_total_blocks(ctx);
diff --git a/tests/fsm/fsm_dealloc_test.err b/tests/fsm/fsm_dealloc_test.err
index 7f413409..aa7db51e 100644
--- a/tests/fsm/fsm_dealloc_test.err
+++ b/tests/fsm/fsm_dealloc_test.err
@@ -1,87 +1,888 @@
 DLGLOBAL DEBUG scene_alloc()
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: is child of test(root)
 DLGLOBAL DEBUG test(_branch0){alive}: Allocated
+DLGLOBAL DEBUG test(_branch0){alive}: is child of test(_branch0)
 DLGLOBAL DEBUG test(_branch0){alive}: Allocated
 DLGLOBAL DEBUG test(_branch0){alive}: is child of test(_branch0)
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: is child of test(root)
+DLGLOBAL DEBUG test(_branch1){alive}: Allocated
+DLGLOBAL DEBUG test(_branch1){alive}: is child of test(_branch1)
+DLGLOBAL DEBUG test(_branch1){alive}: Allocated
+DLGLOBAL DEBUG test(_branch1){alive}: is child of test(_branch1)
 DLGLOBAL DEBUG test(other){alive}: Allocated
 DLGLOBAL DEBUG test(_branch0){alive}: _branch0.other[0] = other
 DLGLOBAL DEBUG test(other){alive}: other.other[0] = _branch0
 DLGLOBAL DEBUG test(__twig0a){alive}: __twig0a.other[0] = other
 DLGLOBAL DEBUG test(other){alive}: other.other[1] = __twig0a
-DLGLOBAL DEBUG --- Test disabled: object 0 was not created. Cleaning up.
-DLGLOBAL DEBUG test(_branch0){alive}: Terminating (cause = OSMO_FSM_TERM_ERROR)
-DLGLOBAL DEBUG test(_branch0){alive}: pre_term()
-DLGLOBAL DEBUG test(__twig0a){alive}: Terminating (cause = OSMO_FSM_TERM_PARENT)
+DLGLOBAL DEBUG test(_branch1){alive}: _branch1.other[0] = other
+DLGLOBAL DEBUG test(other){alive}: other.other[1] = _branch1
+DLGLOBAL DEBUG test(__twig1a){alive}: __twig1a.other[0] = root
+DLGLOBAL DEBUG test(root){alive}: root.other[0] = __twig1a
+DLGLOBAL DEBUG ------ before term cascade, got:
+DLGLOBAL DEBUG   root
+DLGLOBAL DEBUG   _branch0
+DLGLOBAL DEBUG   __twig0a
+DLGLOBAL DEBUG   __twig0b
+DLGLOBAL DEBUG   _branch1
+DLGLOBAL DEBUG   __twig1a
+DLGLOBAL DEBUG   __twig1b
+DLGLOBAL DEBUG   other
+DLGLOBAL DEBUG ---
+DLGLOBAL DEBUG --- term at root
+DLGLOBAL DEBUG test(root){alive}: Terminating (cause = OSMO_FSM_TERM_REGULAR)
+DLGLOBAL DEBUG test(root){alive}: pre_term()
+DLGLOBAL DEBUG test(_branch1){alive}: Terminating in cascade, depth 2 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(_branch1){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig1b){alive}: Terminating in cascade, depth 3 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(__twig1b){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig1b){alive}: Removing from parent test(_branch1)
+DLGLOBAL DEBUG 1 (__twig1b.cleanup())
+DLGLOBAL DEBUG test(__twig1b){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig1b){alive}: scene forgets __twig1b
+DLGLOBAL DEBUG test(_branch1){alive}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 2 (__twig1b.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG test(_branch1){alive}: alive(EV_CHILD_GONE)
+DLGLOBAL DEBUG 3 (__twig1b.cleanup(),_branch1.alive(),_branch1.child_gone())
+DLGLOBAL DEBUG test(_branch1){alive}: EV_CHILD_GONE: Dropped reference _branch1.child[1] = __twig1b
+DLGLOBAL DEBUG test(_branch1){alive}: still exists: child[0]
+DLGLOBAL DEBUG 2 (__twig1b.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG 1 (__twig1b.cleanup())
+DLGLOBAL DEBUG test(__twig1b){alive}: cleanup() done
+DLGLOBAL DEBUG 0 (-)
+DLGLOBAL DEBUG test(__twig1b){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(__twig1a){alive}: Terminating in cascade, depth 3 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(__twig1a){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig1a){alive}: Removing from parent test(_branch1)
+DLGLOBAL DEBUG 1 (__twig1a.cleanup())
+DLGLOBAL DEBUG test(__twig1a){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig1a){alive}: scene forgets __twig1a
+DLGLOBAL DEBUG test(__twig1a){alive}: removing reference __twig1a.other[0] -> root
+DLGLOBAL DEBUG test(root){alive}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 2 (__twig1a.cleanup(),root.alive())
+DLGLOBAL DEBUG test(root){alive}: alive(EV_OTHER_GONE)
+DLGLOBAL DEBUG 3 (__twig1a.cleanup(),root.alive(),root.other_gone())
+DLGLOBAL DEBUG test(root){alive}: EV_OTHER_GONE: Dropped reference root.other[0] = __twig1a
+DLGLOBAL DEBUG 2 (__twig1a.cleanup(),root.alive())
+DLGLOBAL DEBUG test(root){alive}: state_chg to destroying
+DLGLOBAL DEBUG 3 (__twig1a.cleanup(),root.alive(),root.destroying_onenter())
+DLGLOBAL DEBUG test(root){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(root){destroying}: Ignoring trigger to terminate: already terminating
+DLGLOBAL DEBUG 2 (__twig1a.cleanup(),root.alive())
+DLGLOBAL DEBUG 1 (__twig1a.cleanup())
+DLGLOBAL DEBUG test(_branch1){alive}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 2 (__twig1a.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG test(_branch1){alive}: alive(EV_CHILD_GONE)
+DLGLOBAL DEBUG 3 (__twig1a.cleanup(),_branch1.alive(),_branch1.child_gone())
+DLGLOBAL DEBUG test(_branch1){alive}: EV_CHILD_GONE: Dropped reference _branch1.child[0] = __twig1a
+DLGLOBAL DEBUG test(_branch1){alive}: No more children
+DLGLOBAL DEBUG 2 (__twig1a.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG test(_branch1){alive}: state_chg to destroying
+DLGLOBAL DEBUG 3 (__twig1a.cleanup(),_branch1.alive(),_branch1.destroying_onenter())
+DLGLOBAL DEBUG test(_branch1){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(_branch1){destroying}: Ignoring trigger to terminate: already terminating
+DLGLOBAL DEBUG 2 (__twig1a.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG 1 (__twig1a.cleanup())
+DLGLOBAL DEBUG test(__twig1a){alive}: cleanup() done
+DLGLOBAL DEBUG 0 (-)
+DLGLOBAL DEBUG test(__twig1a){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(_branch1){destroying}: Removing from parent test(root)
+DLGLOBAL DEBUG 1 (_branch1.cleanup())
+DLGLOBAL DEBUG test(_branch1){destroying}: cleanup()
+DLGLOBAL DEBUG test(_branch1){destroying}: scene forgets _branch1
+DLGLOBAL DEBUG test(_branch1){destroying}: removing reference _branch1.other[0] -> other
+DLGLOBAL DEBUG test(other){alive}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 2 (_branch1.cleanup(),other.alive())
+DLGLOBAL DEBUG test(other){alive}: alive(EV_OTHER_GONE)
+DLGLOBAL DEBUG 3 (_branch1.cleanup(),other.alive(),other.other_gone())
+DLGLOBAL DEBUG test(other){alive}: EV_OTHER_GONE: Dropped reference other.other[1] = _branch1
+DLGLOBAL DEBUG 2 (_branch1.cleanup(),other.alive())
+DLGLOBAL DEBUG test(other){alive}: state_chg to destroying
+DLGLOBAL DEBUG 3 (_branch1.cleanup(),other.alive(),other.destroying_onenter())
+DLGLOBAL DEBUG test(other){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(other){destroying}: Terminating in cascade, depth 3 (cause = OSMO_FSM_TERM_REGULAR, caused by: test(root))
+DLGLOBAL DEBUG test(other){destroying}: pre_term()
+DLGLOBAL DEBUG 4 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup())
+DLGLOBAL DEBUG test(other){destroying}: cleanup()
+DLGLOBAL DEBUG test(other){destroying}: scene forgets other
+DLGLOBAL DEBUG test(other){destroying}: removing reference other.other[0] -> _branch0
+DLGLOBAL DEBUG test(_branch0){alive}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 5 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG test(_branch0){alive}: alive(EV_OTHER_GONE)
+DLGLOBAL DEBUG 6 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.other_gone())
+DLGLOBAL DEBUG test(_branch0){alive}: EV_OTHER_GONE: Dropped reference _branch0.other[0] = other
+DLGLOBAL DEBUG 5 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG test(_branch0){alive}: state_chg to destroying
+DLGLOBAL DEBUG 6 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter())
+DLGLOBAL DEBUG test(_branch0){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(_branch0){destroying}: Terminating in cascade, depth 4 (cause = OSMO_FSM_TERM_REGULAR, caused by: test(root))
+DLGLOBAL DEBUG test(_branch0){destroying}: pre_term()
+DLGLOBAL DEBUG test(__twig0b){alive}: Terminating in cascade, depth 5 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(__twig0b){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig0b){alive}: Removing from parent test(_branch0)
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(__twig0b){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig0b){alive}: scene forgets __twig0b
+DLGLOBAL DEBUG test(_branch0){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(_branch0){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG 9 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(_branch0){destroying}: EV_CHILD_GONE: Dropped reference _branch0.child[1] = __twig0b
+DLGLOBAL DEBUG test(_branch0){destroying}: still exists: child[0]
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(__twig0b){alive}: cleanup() done
+DLGLOBAL DEBUG 6 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter())
+DLGLOBAL DEBUG test(__twig0b){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(__twig0a){alive}: Terminating in cascade, depth 5 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
 DLGLOBAL DEBUG test(__twig0a){alive}: pre_term()
 DLGLOBAL DEBUG test(__twig0a){alive}: Removing from parent test(_branch0)
-DLGLOBAL DEBUG 1 (__twig0a.cleanup())
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
 DLGLOBAL DEBUG test(__twig0a){alive}: cleanup()
 DLGLOBAL DEBUG test(__twig0a){alive}: scene forgets __twig0a
 DLGLOBAL DEBUG test(__twig0a){alive}: removing reference __twig0a.other[0] -> other
+DLGLOBAL DEBUG test(other){destroying}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(other){destroying}: destroying(EV_OTHER_GONE)
+DLGLOBAL DEBUG 9 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(_branch0){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(_branch0){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG 9 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(_branch0){destroying}: EV_CHILD_GONE: Dropped reference _branch0.child[0] = __twig0a
+DLGLOBAL DEBUG test(_branch0){destroying}: No more children
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(__twig0a){alive}: cleanup() done
+DLGLOBAL DEBUG 6 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter())
+DLGLOBAL DEBUG test(__twig0a){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(_branch0){destroying}: Removing from parent test(root)
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(_branch0){destroying}: cleanup()
+DLGLOBAL DEBUG test(_branch0){destroying}: scene forgets _branch0
+DLGLOBAL DEBUG test(root){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(root){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG 9 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(root){destroying}: EV_CHILD_GONE: Dropped reference root.child[0] = _branch0
+DLGLOBAL DEBUG test(root){destroying}: still exists: child[1]
+DLGLOBAL DEBUG 8 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),_
+DLGLOBAL DEBUG test(_branch0){destroying}: cleanup() done
+DLGLOBAL DEBUG 6 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter())
+DLGLOBAL DEBUG test(root){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 7 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter(),r
+DLGLOBAL DEBUG test(root){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG test(root){destroying}: EV_CHILD_GONE with NULL data, must be a parent_term event. Ignore.
+DLGLOBAL DEBUG 6 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter())
+DLGLOBAL DEBUG test(_branch0){destroying}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG 5 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG 4 (_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup())
+DLGLOBAL DEBUG test(other){destroying}: cleanup() done
+DLGLOBAL DEBUG 3 (_branch1.cleanup(),other.alive(),other.destroying_onenter())
+DLGLOBAL DEBUG test(other){destroying}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG 2 (_branch1.cleanup(),other.alive())
+DLGLOBAL DEBUG 1 (_branch1.cleanup())
+DLGLOBAL DEBUG test(root){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 2 (_branch1.cleanup(),root.destroying())
+DLGLOBAL DEBUG test(root){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG 3 (_branch1.cleanup(),root.destroying(),root.child_gone())
+DLGLOBAL DEBUG test(root){destroying}: EV_CHILD_GONE: Dropped reference root.child[1] = _branch1
+DLGLOBAL DEBUG test(root){destroying}: No more children
+DLGLOBAL DEBUG 2 (_branch1.cleanup(),root.destroying())
+DLGLOBAL DEBUG 1 (_branch1.cleanup())
+DLGLOBAL DEBUG test(_branch1){destroying}: cleanup() done
+DLGLOBAL DEBUG 0 (-)
+DLGLOBAL DEBUG test(_branch1){destroying}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG 1 (root.cleanup())
+DLGLOBAL DEBUG test(root){destroying}: cleanup()
+DLGLOBAL DEBUG test(root){destroying}: scene forgets root
+DLGLOBAL DEBUG test(root){destroying}: cleanup() done
+DLGLOBAL DEBUG 0 (-)
+DLGLOBAL DEBUG test(root){destroying}: Deallocated, including all deferred deallocations
+DLGLOBAL DEBUG --- after term cascade:
+DLGLOBAL DEBUG --- all deallocated.
+DLGLOBAL DEBUG scene_alloc()
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: is child of test(root)
+DLGLOBAL DEBUG test(_branch0){alive}: Allocated
+DLGLOBAL DEBUG test(_branch0){alive}: is child of test(_branch0)
+DLGLOBAL DEBUG test(_branch0){alive}: Allocated
+DLGLOBAL DEBUG test(_branch0){alive}: is child of test(_branch0)
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: is child of test(root)
+DLGLOBAL DEBUG test(_branch1){alive}: Allocated
+DLGLOBAL DEBUG test(_branch1){alive}: is child of test(_branch1)
+DLGLOBAL DEBUG test(_branch1){alive}: Allocated
+DLGLOBAL DEBUG test(_branch1){alive}: is child of test(_branch1)
+DLGLOBAL DEBUG test(other){alive}: Allocated
+DLGLOBAL DEBUG test(_branch0){alive}: _branch0.other[0] = other
+DLGLOBAL DEBUG test(other){alive}: other.other[0] = _branch0
+DLGLOBAL DEBUG test(__twig0a){alive}: __twig0a.other[0] = other
+DLGLOBAL DEBUG test(other){alive}: other.other[1] = __twig0a
+DLGLOBAL DEBUG test(_branch1){alive}: _branch1.other[0] = other
+DLGLOBAL DEBUG test(other){alive}: other.other[1] = _branch1
+DLGLOBAL DEBUG test(__twig1a){alive}: __twig1a.other[0] = root
+DLGLOBAL DEBUG test(root){alive}: root.other[0] = __twig1a
+DLGLOBAL DEBUG ------ before destroy-event cascade, got:
+DLGLOBAL DEBUG   root
+DLGLOBAL DEBUG   _branch0
+DLGLOBAL DEBUG   __twig0a
+DLGLOBAL DEBUG   __twig0b
+DLGLOBAL DEBUG   _branch1
+DLGLOBAL DEBUG   __twig1a
+DLGLOBAL DEBUG   __twig1b
+DLGLOBAL DEBUG   other
+DLGLOBAL DEBUG ---
+DLGLOBAL DEBUG --- destroy-event at root
+DLGLOBAL DEBUG test(root){alive}: Received Event EV_DESTROY
+DLGLOBAL DEBUG 1 (root.alive())
+DLGLOBAL DEBUG test(root){alive}: alive(EV_DESTROY)
+DLGLOBAL DEBUG test(root){alive}: state_chg to destroying
+DLGLOBAL DEBUG 2 (root.alive(),root.destroying_onenter())
+DLGLOBAL DEBUG test(root){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(root){destroying}: Terminating (cause = OSMO_FSM_TERM_REGULAR)
+DLGLOBAL DEBUG test(root){destroying}: pre_term()
+DLGLOBAL DEBUG test(_branch1){alive}: Terminating in cascade, depth 2 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(_branch1){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig1b){alive}: Terminating in cascade, depth 3 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(__twig1b){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig1b){alive}: Removing from parent test(_branch1)
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),__twig1b.cleanup())
+DLGLOBAL DEBUG test(__twig1b){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig1b){alive}: scene forgets __twig1b
+DLGLOBAL DEBUG test(_branch1){alive}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),__twig1b.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG test(_branch1){alive}: alive(EV_CHILD_GONE)
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),__twig1b.cleanup(),_branch1.alive(),_branch1.child_gone())
+DLGLOBAL DEBUG test(_branch1){alive}: EV_CHILD_GONE: Dropped reference _branch1.child[1] = __twig1b
+DLGLOBAL DEBUG test(_branch1){alive}: still exists: child[0]
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),__twig1b.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),__twig1b.cleanup())
+DLGLOBAL DEBUG test(__twig1b){alive}: cleanup() done
+DLGLOBAL DEBUG 2 (root.alive(),root.destroying_onenter())
+DLGLOBAL DEBUG test(__twig1b){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(__twig1a){alive}: Terminating in cascade, depth 3 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(__twig1a){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig1a){alive}: Removing from parent test(_branch1)
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),__twig1a.cleanup())
+DLGLOBAL DEBUG test(__twig1a){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig1a){alive}: scene forgets __twig1a
+DLGLOBAL DEBUG test(__twig1a){alive}: removing reference __twig1a.other[0] -> root
+DLGLOBAL DEBUG test(root){destroying}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),root.destroying())
+DLGLOBAL DEBUG test(root){destroying}: destroying(EV_OTHER_GONE)
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),root.destroying(),root.other_gone())
+DLGLOBAL DEBUG test(root){destroying}: EV_OTHER_GONE: Dropped reference root.other[0] = __twig1a
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),root.destroying())
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),__twig1a.cleanup())
+DLGLOBAL DEBUG test(_branch1){alive}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG test(_branch1){alive}: alive(EV_CHILD_GONE)
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),_branch1.alive(),_branch1.child_gone())
+DLGLOBAL DEBUG test(_branch1){alive}: EV_CHILD_GONE: Dropped reference _branch1.child[0] = __twig1a
+DLGLOBAL DEBUG test(_branch1){alive}: No more children
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG test(_branch1){alive}: state_chg to destroying
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),_branch1.alive(),_branch1.destroying_onenter())
+DLGLOBAL DEBUG test(_branch1){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(_branch1){destroying}: Ignoring trigger to terminate: already terminating
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),__twig1a.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),__twig1a.cleanup())
+DLGLOBAL DEBUG test(__twig1a){alive}: cleanup() done
+DLGLOBAL DEBUG 2 (root.alive(),root.destroying_onenter())
+DLGLOBAL DEBUG test(__twig1a){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(_branch1){destroying}: Removing from parent test(root)
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),_branch1.cleanup())
+DLGLOBAL DEBUG test(_branch1){destroying}: cleanup()
+DLGLOBAL DEBUG test(_branch1){destroying}: scene forgets _branch1
+DLGLOBAL DEBUG test(_branch1){destroying}: removing reference _branch1.other[0] -> other
 DLGLOBAL DEBUG test(other){alive}: Received Event EV_OTHER_GONE
-DLGLOBAL DEBUG 2 (__twig0a.cleanup(),other.alive())
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive())
 DLGLOBAL DEBUG test(other){alive}: alive(EV_OTHER_GONE)
-DLGLOBAL DEBUG 3 (__twig0a.cleanup(),other.alive(),other.other_gone())
-DLGLOBAL DEBUG test(other){alive}: EV_OTHER_GONE: Dropped reference other.other[1] = __twig0a
-DLGLOBAL DEBUG 2 (__twig0a.cleanup(),other.alive())
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.other_gone())
+DLGLOBAL DEBUG test(other){alive}: EV_OTHER_GONE: Dropped reference other.other[1] = _branch1
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive())
 DLGLOBAL DEBUG test(other){alive}: state_chg to destroying
-DLGLOBAL DEBUG 3 (__twig0a.cleanup(),other.alive(),other.destroying_onenter())
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter())
 DLGLOBAL DEBUG test(other){destroying}: destroying_onenter() from alive
-DLGLOBAL DEBUG test(other){destroying}: Terminating (cause = OSMO_FSM_TERM_REGULAR)
+DLGLOBAL DEBUG test(other){destroying}: Terminating in cascade, depth 3 (cause = OSMO_FSM_TERM_REGULAR, caused by: test(root))
 DLGLOBAL DEBUG test(other){destroying}: pre_term()
-DLGLOBAL DEBUG 4 (__twig0a.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup())
+DLGLOBAL DEBUG 6 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup())
 DLGLOBAL DEBUG test(other){destroying}: cleanup()
 DLGLOBAL DEBUG test(other){destroying}: scene forgets other
 DLGLOBAL DEBUG test(other){destroying}: removing reference other.other[0] -> _branch0
 DLGLOBAL DEBUG test(_branch0){alive}: Received Event EV_OTHER_GONE
-DLGLOBAL DEBUG 5 (__twig0a.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG 7 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
 DLGLOBAL DEBUG test(_branch0){alive}: alive(EV_OTHER_GONE)
-DLGLOBAL DEBUG 6 (__twig0a.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.other_gone())
+DLGLOBAL DEBUG 8 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
 DLGLOBAL DEBUG test(_branch0){alive}: EV_OTHER_GONE: Dropped reference _branch0.other[0] = other
-DLGLOBAL DEBUG 5 (__twig0a.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG 7 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
 DLGLOBAL DEBUG test(_branch0){alive}: state_chg to destroying
-DLGLOBAL DEBUG 6 (__twig0a.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive(),_branch0.destroying_onenter())
+DLGLOBAL DEBUG 8 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
 DLGLOBAL DEBUG test(_branch0){destroying}: destroying_onenter() from alive
-DLGLOBAL DEBUG test(_branch0){destroying}: Ignoring trigger to terminate: already terminating
-DLGLOBAL DEBUG 5 (__twig0a.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.alive())
-DLGLOBAL DEBUG 4 (__twig0a.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup())
-DLGLOBAL DEBUG test(other){destroying}: cleanup() done
-DLGLOBAL DEBUG 3 (__twig0a.cleanup(),other.alive(),other.destroying_onenter())
-DLGLOBAL DEBUG test(other){destroying}: Freeing instance
-DLGLOBAL DEBUG test(other){destroying}: Deallocated
-DLGLOBAL DEBUG 2 (__twig0a.cleanup(),other.alive())
-DLGLOBAL DEBUG 1 (__twig0a.cleanup())
+DLGLOBAL DEBUG test(_branch0){destroying}: Terminating in cascade, depth 4 (cause = OSMO_FSM_TERM_REGULAR, caused by: test(root))
+DLGLOBAL DEBUG test(_branch0){destroying}: pre_term()
+DLGLOBAL DEBUG test(__twig0b){alive}: Terminating in cascade, depth 5 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(__twig0b){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig0b){alive}: Removing from parent test(_branch0)
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(__twig0b){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig0b){alive}: scene forgets __twig0b
 DLGLOBAL DEBUG test(_branch0){destroying}: Received Event EV_CHILD_GONE
-DLGLOBAL DEBUG 2 (__twig0a.cleanup(),_branch0.destroying())
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
 DLGLOBAL DEBUG test(_branch0){destroying}: destroying(EV_CHILD_GONE)
-DLGLOBAL DEBUG 3 (__twig0a.cleanup(),_branch0.destroying(),_branch0.child_gone())
+DLGLOBAL DEBUG 11 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG test(_branch0){destroying}: EV_CHILD_GONE: Dropped reference _branch0.child[1] = __twig0b
+DLGLOBAL DEBUG test(_branch0){destroying}: still exists: child[0]
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(__twig0b){alive}: cleanup() done
+DLGLOBAL DEBUG 8 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(__twig0b){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(__twig0a){alive}: Terminating in cascade, depth 5 (cause = OSMO_FSM_TERM_PARENT, caused by: test(root))
+DLGLOBAL DEBUG test(__twig0a){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig0a){alive}: Removing from parent test(_branch0)
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(__twig0a){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig0a){alive}: scene forgets __twig0a
+DLGLOBAL DEBUG test(__twig0a){alive}: removing reference __twig0a.other[0] -> other
+DLGLOBAL DEBUG test(other){destroying}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG test(other){destroying}: destroying(EV_OTHER_GONE)
+DLGLOBAL DEBUG 11 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(_branch0){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG test(_branch0){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG 11 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
 DLGLOBAL DEBUG test(_branch0){destroying}: EV_CHILD_GONE: Dropped reference _branch0.child[0] = __twig0a
 DLGLOBAL DEBUG test(_branch0){destroying}: No more children
-DLGLOBAL DEBUG 2 (__twig0a.cleanup(),_branch0.destroying())
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(__twig0a){alive}: cleanup() done
+DLGLOBAL DEBUG 8 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(__twig0a){alive}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG test(_branch0){destroying}: Removing from parent test(root)
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(_branch0){destroying}: cleanup()
+DLGLOBAL DEBUG test(_branch0){destroying}: scene forgets _branch0
+DLGLOBAL DEBUG test(root){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG test(root){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG 11 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG test(root){destroying}: EV_CHILD_GONE: Dropped reference root.child[0] = _branch0
+DLGLOBAL DEBUG test(root){destroying}: still exists: child[1]
+DLGLOBAL DEBUG 10 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(_branch0){destroying}: cleanup() done
+DLGLOBAL DEBUG 8 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(root){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 9 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(root){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG test(root){destroying}: EV_CHILD_GONE with NULL data, must be a parent_term event. Ignore.
+DLGLOBAL DEBUG 8 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG test(_branch0){destroying}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG 7 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch0.
+DLGLOBAL DEBUG 6 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup())
+DLGLOBAL DEBUG test(other){destroying}: cleanup() done
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive(),other.destroying_onenter())
+DLGLOBAL DEBUG test(other){destroying}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),other.alive())
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),_branch1.cleanup())
+DLGLOBAL DEBUG test(root){destroying}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),root.destroying())
+DLGLOBAL DEBUG test(root){destroying}: destroying(EV_CHILD_GONE)
+DLGLOBAL DEBUG 5 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),root.destroying(),root.child_gone())
+DLGLOBAL DEBUG test(root){destroying}: EV_CHILD_GONE: Dropped reference root.child[1] = _branch1
+DLGLOBAL DEBUG test(root){destroying}: No more children
+DLGLOBAL DEBUG 4 (root.alive(),root.destroying_onenter(),_branch1.cleanup(),root.destroying())
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),_branch1.cleanup())
+DLGLOBAL DEBUG test(_branch1){destroying}: cleanup() done
+DLGLOBAL DEBUG 2 (root.alive(),root.destroying_onenter())
+DLGLOBAL DEBUG test(_branch1){destroying}: Deferring: will deallocate with test(root)
+DLGLOBAL DEBUG 3 (root.alive(),root.destroying_onenter(),root.cleanup())
+DLGLOBAL DEBUG test(root){destroying}: cleanup()
+DLGLOBAL DEBUG test(root){destroying}: scene forgets root
+DLGLOBAL DEBUG test(root){destroying}: cleanup() done
+DLGLOBAL DEBUG 2 (root.alive(),root.destroying_onenter())
+DLGLOBAL DEBUG test(root){destroying}: Deallocated, including all deferred deallocations
+DLGLOBAL DEBUG 1 (root.alive())
+DLGLOBAL DEBUG 0 (-)
+DLGLOBAL DEBUG --- after destroy-event cascade:
+DLGLOBAL DEBUG --- all deallocated.
+DLGLOBAL DEBUG scene_alloc()
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: is child of test(root)
+DLGLOBAL DEBUG test(_branch0){alive}: Allocated
+DLGLOBAL DEBUG test(_branch0){alive}: is child of test(_branch0)
+DLGLOBAL DEBUG test(_branch0){alive}: Allocated
+DLGLOBAL DEBUG test(_branch0){alive}: is child of test(_branch0)
+DLGLOBAL DEBUG test(root){alive}: Allocated
+DLGLOBAL DEBUG test(root){alive}: is child of test(root)
+DLGLOBAL DEBUG test(_branch1){alive}: Allocated
+DLGLOBAL DEBUG test(_branch1){alive}: is child of test(_branch1)
+DLGLOBAL DEBUG test(_branch1){alive}: Allocated
+DLGLOBAL DEBUG test(_branch1){alive}: is child of test(_branch1)
+DLGLOBAL DEBUG test(other){alive}: Allocated
+DLGLOBAL DEBUG test(_branch0){alive}: _branch0.other[0] = other
+DLGLOBAL DEBUG test(other){alive}: other.other[0] = _branch0
+DLGLOBAL DEBUG test(__twig0a){alive}: __twig0a.other[0] = other
+DLGLOBAL DEBUG test(other){alive}: other.other[1] = __twig0a
+DLGLOBAL DEBUG test(_branch1){alive}: _branch1.other[0] = other
+DLGLOBAL DEBUG test(other){alive}: other.other[1] = _branch1
+DLGLOBAL DEBUG test(__twig1a){alive}: __twig1a.other[0] = root
+DLGLOBAL DEBUG test(root){alive}: root.other[0] = __twig1a
+DLGLOBAL DEBUG ------ before term cascade, got:
+DLGLOBAL DEBUG   root
+DLGLOBAL DEBUG   _branch0
+DLGLOBAL DEBUG   __twig0a
+DLGLOBAL DEBUG   __twig0b
+DLGLOBAL DEBUG   _branch1
+DLGLOBAL DEBUG   __twig1a
+DLGLOBAL DEBUG   __twig1b
+DLGLOBAL DEBUG   other
+DLGLOBAL DEBUG ---
+DLGLOBAL DEBUG --- term at _branch0
+DLGLOBAL DEBUG test(_branch0){alive}: Terminating (cause = OSMO_FSM_TERM_REGULAR)
+DLGLOBAL DEBUG test(_branch0){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig0b){alive}: Terminating in cascade, depth 2 (cause = OSMO_FSM_TERM_PARENT, caused by: test(_branch0))
+DLGLOBAL DEBUG test(__twig0b){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig0b){alive}: Removing from parent test(_branch0)
+DLGLOBAL DEBUG 1 (__twig0b.cleanup())
+DLGLOBAL DEBUG test(__twig0b){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig0b){alive}: scene forgets __twig0b
+DLGLOBAL DEBUG test(_branch0){alive}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 2 (__twig0b.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG test(_branch0){alive}: alive(EV_CHILD_GONE)
+DLGLOBAL DEBUG 3 (__twig0b.cleanup(),_branch0.alive(),_branch0.child_gone())
+DLGLOBAL DEBUG test(_branch0){alive}: EV_CHILD_GONE: Dropped reference _branch0.child[1] = __twig0b
+DLGLOBAL DEBUG test(_branch0){alive}: still exists: child[0]
+DLGLOBAL DEBUG 2 (__twig0b.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG 1 (__twig0b.cleanup())
+DLGLOBAL DEBUG test(__twig0b){alive}: cleanup() done
+DLGLOBAL DEBUG 0 (-)
+DLGLOBAL DEBUG test(__twig0b){alive}: Deferring: will deallocate with test(_branch0)
+DLGLOBAL DEBUG test(__twig0a){alive}: Terminating in cascade, depth 2 (cause = OSMO_FSM_TERM_PARENT, caused by: test(_branch0))
+DLGLOBAL DEBUG test(__twig0a){alive}: pre_term()
+DLGLOBAL DEBUG test(__twig0a){alive}: Removing from parent test(_branch0)
+DLGLOBAL DEBUG 1 (__twig0a.cleanup())
+DLGLOBAL DEBUG test(__twig0a){alive}: cleanup()
+DLGLOBAL DEBUG test(__twig0a){alive}: scene forgets __twig0a
+DLGLOBAL DEBUG test(__twig0a){alive}: removing reference __twig0a.other[0] -> other
+DLGLOBAL DEBUG test(other){alive}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 2 (__twig0a.cleanup(),other.alive())
+DLGLOBAL DEBUG test(other){alive}: alive(EV_OTHER_GONE)
+DLGLOBAL DEBUG 3 (__twig0a.cleanup(),other.alive(),other.other_gone())
+DLGLOBAL DEBUG 2 (__twig0a.cleanup(),other.alive())
+DLGLOBAL DEBUG 1 (__twig0a.cleanup())
+DLGLOBAL DEBUG test(_branch0){alive}: Received Event EV_CHILD_GONE
+DLGLOBAL DEBUG 2 (__twig0a.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG test(_branch0){alive}: alive(EV_CHILD_GONE)
+DLGLOBAL DEBUG 3 (__twig0a.cleanup(),_branch0.alive(),_branch0.child_gone())
+DLGLOBAL DEBUG test(_branch0){alive}: EV_CHILD_GONE: Dropped reference _branch0.child[0] = __twig0a
+DLGLOBAL DEBUG test(_branch0){alive}: No more children
+DLGLOBAL DEBUG 2 (__twig0a.cleanup(),_branch0.alive())
+DLGLOBAL DEBUG test(_branch0){alive}: state_chg to destroying
+DLGLOBAL DEBUG 3 (__twig0a.cleanup(),_branch0.alive(),_branch0.destroying_onenter())
+DLGLOBAL DEBUG test(_branch0){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(_branch0){destroying}: Ignoring trigger to terminate: already terminating
+DLGLOBAL DEBUG 2 (__twig0a.cleanup(),_branch0.alive())
 DLGLOBAL DEBUG 1 (__twig0a.cleanup())
 DLGLOBAL DEBUG test(__twig0a){alive}: cleanup() done
 DLGLOBAL DEBUG 0 (-)
-DLGLOBAL DEBUG test(__twig0a){alive}: Freeing instance
-DLGLOBAL DEBUG test(__twig0a){alive}: Deallocated
+DLGLOBAL DEBUG test(__twig0a){alive}: Deferring: will deallocate with test(_branch0)
+DLGLOBAL DEBUG test(_branch0){destroying}: Removing from parent test(root)
 DLGLOBAL DEBUG 1 (_branch0.cleanup())
 DLGLOBAL DEBUG test(_branch0){destroying}: cleanup()
 DLGLOBAL DEBUG test(_branch0){destroying}: scene forgets _branch0
+DLGLOBAL DEBUG test(_branch0){destroying}: removing reference _branch0.other[0] -> other
+DLGLOBAL DEBUG test(other){alive}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 2 (_branch0.cleanup(),other.alive())
+DLGLOBAL DEBUG test(other){alive}: alive(EV_OTHER_GONE)
+DLGLOBAL DEBUG 3 (_branch0.cleanup(),other.alive(),other.other_gone())
+DLGLOBAL DEBUG test(other){alive}: EV_OTHER_GONE: Dropped reference other.other[0] = _branch0
+DLGLOBAL DEBUG 2 (_branch0.cleanup(),other.alive())
+DLGLOBAL DEBUG test(other){alive}: state_chg to destroying
+DLGLOBAL DEBUG 3 (_branch0.cleanup(),other.alive(),other.destroying_onenter())
+DLGLOBAL DEBUG test(other){destroying}: destroying_onenter() from alive
+DLGLOBAL DEBUG test(other){destroying}: Terminating in cascade, depth 2 (cause = OSMO_FSM_TERM_REGULAR, caused by: test(_branch0))
+DLGLOBAL DEBUG test(other){destroying}: pre_term()
+DLGLOBAL DEBUG 4 (_branch0.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup())
+DLGLOBAL DEBUG test(other){destroying}: cleanup()
+DLGLOBAL DEBUG test(other){destroying}: scene forgets other
+DLGLOBAL DEBUG test(other){destroying}: removing reference other.other[1] -> _branch1
+DLGLOBAL DEBUG test(_branch1){alive}: Received Event EV_OTHER_GONE
+DLGLOBAL DEBUG 5 (_branch0.cleanup(),other.alive(),other.destroying_onenter(),other.cleanup(),_branch1.alive())
+DLGLOBAL DEBUG test(_branch1){alive}: alive(EV_OTHER_GONE)
+DLGLOBAL DEBUG 6 (_branch0.cleanup(),other.alive(),other.des