Give the _sends member of InternalReturn its own mutex,

rather than using the process lock to protect it.  Prevents
a deadlock when removing an aux send causes it to remove
itself from its return (#4712).


git-svn-id: svn://localhost/ardour2/branches/3.0@11760 d708f5d6-7413-0410-9779-e7cbd77b26cf

3 files changed, 11 insertions, 12 deletions

diff --git a/libs/ardour/ardour/internal_return.h b/libs/ardour/ardour/internal_return.h
index 1dff465cba..291b51896c 100644
--- a/libs/ardour/ardour/internal_return.h
+++ b/libs/ardour/ardour/internal_return.h
@@ -47,6 +47,8 @@ class InternalReturn : public Return
   private:
 	/** sends that we are receiving data from */
 	std::list<InternalSend*> _sends;
+	/** mutex to protect _sends */
+	Glib::Mutex _sends_mutex;
 };
 
 } // namespace ARDOUR
diff --git a/libs/ardour/internal_return.cc b/libs/ardour/internal_return.cc
index 3c75c7957d..6a3d20e5c9 100644
--- a/libs/ardour/internal_return.cc
+++ b/libs/ardour/internal_return.cc
@@ -43,11 +43,13 @@ InternalReturn::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*e
 		return;
 	}
 
-	/* _sends is only modified with the process lock held, so this is ok, I think */
-
-	for (list<InternalSend*>::iterator i = _sends.begin(); i != _sends.end(); ++i) {
-		if ((*i)->active ()) {
-			bufs.merge_from ((*i)->get_buffers(), nframes);
+	Glib::Mutex::Lock lm (_sends_mutex, Glib::TRY_LOCK);
+	
+	if (lm.locked ()) {
+		for (list<InternalSend*>::iterator i = _sends.begin(); i != _sends.end(); ++i) {
+			if ((*i)->active ()) {
+				bufs.merge_from ((*i)->get_buffers(), nframes);
+			}
 		}
 	}
 
@@ -57,18 +59,14 @@ InternalReturn::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*e
 void
 InternalReturn::add_send (InternalSend* send)
 {
-	/* caller must hold process lock */
-	assert (!AudioEngine::instance()->process_lock().trylock());
-
+	Glib::Mutex::Lock lm (_sends_mutex);
 	_sends.push_back (send);
 }
 
 void
 InternalReturn::remove_send (InternalSend* send)
 {
-	/* caller must hold process lock */
-	assert (!AudioEngine::instance()->process_lock().trylock());
-
+	Glib::Mutex::Lock lm (_sends_mutex);
 	_sends.remove (send);
 }
 
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index f5bd4dc636..3cb71fad84 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -2606,7 +2606,6 @@ Route::add_send_to_internal_return (InternalSend* send)
 void
 Route::remove_send_from_internal_return (InternalSend* send)
 {
-	Glib::Mutex::Lock lm (AudioEngine::instance()->process_lock ());
 	Glib::RWLock::ReaderLock rm (_processor_lock);
 
 	for (ProcessorList::const_iterator x = _processors.begin(); x != _processors.end(); ++x) {