Add a trash pool for invalidation requests.

While EventLoop::invalidate_request() does invalidate request in the
request-list. It does *not* invalidate requests in the
per-thread-request-ringbuffer(s).
The invalidation record cannot be deleted in EventLoop::invalidate_request
see 6b5891a78f.

3 files changed, 22 insertions, 6 deletions

diff --git a/libs/pbd/event_loop.cc b/libs/pbd/event_loop.cc
index 0baba2835a..aae0c21a08 100644
--- a/libs/pbd/event_loop.cc
+++ b/libs/pbd/event_loop.cc
@@ -95,8 +95,9 @@ EventLoop::invalidate_request (void* data)
 				(*i)->invalidation = 0;
 			}
 		}
-		// should this not always be deleted, regardless if there's an event_loop?
-		delete ir;
+		// This invalidation record may still be in-use in per-thread-request-ringbuffer.
+		// it cannot be deleted here,
+		ir->event_loop->trash.push_back(ir);
 	} else {
 		DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("EventLoop::invalidate_request no event-loop for invalidation %1\n", ir));
 	}
diff --git a/libs/pbd/pbd/abstract_ui.cc b/libs/pbd/pbd/abstract_ui.cc
index db63c3f96d..db7ce38a64 100644
--- a/libs/pbd/pbd/abstract_ui.cc
+++ b/libs/pbd/pbd/abstract_ui.cc
@@ -218,6 +218,7 @@ AbstractUI<RequestObject>::handle_ui_requests ()
 			if (vec.len[0] == 0) {
 				break;
 			} else {
+				bool alive = true;
 				if (vec.buf[0]->valid ()) {
 					/* We first need to remove the event from the list.
 					 * If the event results in object destruction, PBD::EventLoop::invalidate_request
@@ -225,6 +226,7 @@ AbstractUI<RequestObject>::handle_ui_requests ()
 					 */
 					DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: remove request %2 from its invalidation list %3\n", event_loop_name(), vec.buf[0], vec.buf[0]->invalidation));
 					if (vec.buf[0]->invalidation) {
+						alive = std::find (trash.begin(), trash.end(), vec.buf[0]->invalidation) == trash.end();
 						DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: removing invalidation record for that request\n", event_loop_name()));
 						if (vec.buf[0]->invalidation->event_loop && vec.buf[0]->invalidation->event_loop != this) {
 							vec.buf[0]->invalidation->event_loop->slot_invalidation_mutex().lock ();
@@ -240,8 +242,12 @@ AbstractUI<RequestObject>::handle_ui_requests ()
 					DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: valid request, unlocking before calling\n", event_loop_name()));
 					rbml.release ();
 
-					DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: valid request, calling ::do_request()\n", event_loop_name()));
-					do_request (vec.buf[0]);
+					if (alive) {
+						DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: valid request, calling ::do_request()\n", event_loop_name()));
+						do_request (vec.buf[0]);
+					} else {
+						DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: skipping invalidated request\n", event_loop_name()));
+					}
 
 					/* if the request was CallSlot, then we need to ensure that we reset the functor in the request, in case it
 					 * held a shared_ptr<>. Failure to do so can lead to dangling references to objects passed to PBD::Signals.
@@ -264,8 +270,6 @@ AbstractUI<RequestObject>::handle_ui_requests ()
 		}
 	}
 
-	/* clean up any dead request buffers (their thread has exited) */
-
 	assert (rbml.locked ());
 	for (i = request_buffers.begin(); i != request_buffers.end(); ) {
 		if ((*i).second->dead) {
@@ -370,6 +374,15 @@ AbstractUI<RequestObject>::handle_ui_requests ()
 		rbml.acquire();
 	}
 
+	/* clean up any dead invalidation records (object was deleted) */
+	trash.sort();
+	trash.unique();
+	for (std::list<InvalidationRecord*>::const_iterator r = trash.begin(); r != trash.end(); ++r) {
+		DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1 drop invalidation trash %2\n", event_loop_name(), *r));
+		delete *r;
+	}
+	trash.clear ();
+
 	rbml.release ();
 }
 
diff --git a/libs/pbd/pbd/event_loop.h b/libs/pbd/pbd/event_loop.h
index 6fd92c49c8..e84832ebcb 100644
--- a/libs/pbd/pbd/event_loop.h
+++ b/libs/pbd/pbd/event_loop.h
@@ -99,6 +99,8 @@ public:
 	static void pre_register (const std::string& emitting_thread_name, uint32_t num_requests);
 	static void remove_request_buffer_from_map (void* ptr);
 
+	std::list<InvalidationRecord*> trash;
+
 private:
 	static Glib::Threads::Private<EventLoop> thread_event_loop;
 	std::string _name;