session: add signal to indicate batch updates

[ardour.git] / libs / ardour / session_process.cc

diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index d65fe3d56d72c5739ce41f70a0342ca7f54cb402..404f06128f8bcafee88f7ca89bd00692a31bfd4b 100644 (file)
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -75,7 +75,7 @@ Session::process (pframes_t nframes)
 
        (this->*process_function) (nframes);
 
-       /* realtime-safe meter-position changes
+       /* realtime-safe meter-position and processor-order changes
         *
         * ideally this would be done in
         * Route::process_output_buffers() but various functions
@@ -83,7 +83,19 @@ Session::process (pframes_t nframes)
         */
        boost::shared_ptr<RouteList> r = routes.reader ();
        for (RouteList::const_iterator i = r->begin(); i != r->end(); ++i) {
-               (*i)->apply_processor_changes_rt();
+               if ((*i)->apply_processor_changes_rt()) {
+                       _rt_emit_pending = true;
+               }
+       }
+       if (_rt_emit_pending) {
+               if (!_rt_thread_active) {
+                       emit_route_signals ();
+               }
+               if (pthread_mutex_trylock (&_rt_emit_mutex) == 0) {
+                       pthread_cond_signal (&_rt_emit_cond);
+                       pthread_mutex_unlock (&_rt_emit_mutex);
+                       _rt_emit_pending = false;
+               }
        }
 
        _engine.main_thread()->drop_buffers ();
@@ -1226,3 +1238,79 @@ Session::compute_stop_limit () const
 
        return current_end_frame ();
 }
+
+
+
+/* dedicated thread for signal emission.
+ *
+ * while sending cross-thread signals from the process thread
+ * is fine in general, PBD::Signal's use of boost::function and
+ * boost:bind can produce a vast overhead which is not
+ * acceptable for low latency.
+ *
+ * This works around the issue by moving the boost overhead
+ * out of the RT thread. The overall load is probably higher but
+ * the realtime thread remains unaffected.
+ */
+
+void
+Session::emit_route_signals ()
+{
+       // TODO use RAII to allow using these signals in other places
+       BatchUpdateStart(); /* EMIT SIGNAL */
+       boost::shared_ptr<RouteList> r = routes.reader ();
+       for (RouteList::const_iterator ci = r->begin(); ci != r->end(); ++ci) {
+               (*ci)->emit_pending_signals ();
+       }
+       BatchUpdateEnd(); /* EMIT SIGNAL */
+}
+
+void
+Session::emit_thread_start ()
+{
+       if (_rt_thread_active) {
+               return;
+       }
+       _rt_thread_active = true;
+
+       if (pthread_create (&_rt_emit_thread, NULL, emit_thread, this)) {
+               _rt_thread_active = false;
+       }
+}
+
+void
+Session::emit_thread_terminate ()
+{
+       if (!_rt_thread_active) {
+               return;
+       }
+       _rt_thread_active = false;
+
+       if (pthread_mutex_lock (&_rt_emit_mutex) == 0) {
+               pthread_cond_signal (&_rt_emit_cond);
+               pthread_mutex_unlock (&_rt_emit_mutex);
+       }
+
+       void *status;
+       pthread_join (_rt_emit_thread, &status);
+}
+
+void *
+Session::emit_thread (void *arg)
+{
+       Session *s = static_cast<Session *>(arg);
+       s->emit_thread_run ();
+       pthread_exit (0);
+       return 0;
+}
+
+void
+Session::emit_thread_run ()
+{
+       pthread_mutex_lock (&_rt_emit_mutex);
+       while (_rt_thread_active) {
+               emit_route_signals();
+               pthread_cond_wait (&_rt_emit_cond, &_rt_emit_mutex);
+       }
+       pthread_mutex_unlock (&_rt_emit_mutex);
+}