Fix crash when aborting export.

The "Stop" button results in ExportHandlerPtr being destroyed.
This must not happen while it's in use -- in particular during
ExportHandler::start_timespan() and ExportHandler::finish_timespan()

libs/ardour/ardour/export_status.h

@@ -39,17 +39,22 @@ class LIBARDOUR_API ExportStatus {
 	/* Status info */
 
 	volatile bool           stop;
-	volatile bool           running;
 
 	void abort (bool error_occurred = false);
 	bool aborted () const { return _aborted; }
 	bool errors () const { return _errors; }
+	bool running () const { return _running; }
+
+	void set_running (bool r) {
+		assert (!_run_lock.trylock()); // must hold lock
+		_running = r;
+	}
+	Glib::Threads::Mutex& lock () { return _run_lock; }
 
 	PBD::Signal0<void>      Finished;
 	void finish ();
-	bool finished () const { return _finished; }
 
-        void cleanup ();
+	void cleanup ();
 
 	/* Progress info */
 
@@ -77,8 +82,9 @@ class LIBARDOUR_API ExportStatus {
   private:
 	volatile bool          _aborted;
 	volatile bool          _errors;
-	volatile bool          _finished;
+	volatile bool          _running;
 
+	Glib::Threads::Mutex   _run_lock;
 };
 
 } // namespace ARDOUR

libs/ardour/export_handler.cc

@@ -150,6 +150,7 @@ ExportHandler::do_export ()
 
 	/* Start export */
 
+	Glib::Threads::Mutex::Lock l (export_status->lock());
 	start_timespan ();
 }
 
@@ -160,7 +161,7 @@ ExportHandler::start_timespan ()
 
 	if (config_map.empty()) {
 		// freewheeling has to be stopped from outside the process cycle
-		export_status->running = false;
+		export_status->set_running (false);
 		return;
 	}
 
@@ -219,11 +220,13 @@ ExportHandler::handle_duplicate_format_extensions()
 int
 ExportHandler::process (framecnt_t frames)
 {
-	if (!export_status->running) {
+	if (!export_status->running ()) {
 		return 0;
 	} else if (normalizing) {
+		Glib::Threads::Mutex::Lock l (export_status->lock());
 		return process_normalize ();
 	} else {
+		Glib::Threads::Mutex::Lock l (export_status->lock());
 		return process_timespan (frames);
 	}
 }

libs/ardour/export_status.cc

@@ -33,10 +33,10 @@ ExportStatus::ExportStatus ()
 void
 ExportStatus::init ()
 {
+	Glib::Threads::Mutex::Lock l (_run_lock);
 	stop = false;
-	running = false;
+	_running = false;
 	_aborted = false;
-	_finished = false;
 	_errors = false;
 
 	active_job = Exporting;
@@ -57,17 +57,17 @@ ExportStatus::init ()
 void
 ExportStatus::abort (bool error_occurred)
 {
+	Glib::Threads::Mutex::Lock l (_run_lock);
 	_aborted = true;
-	_finished = true;
 	_errors = _errors || error_occurred;
-	running = false;
+	_running = false;
 }
 
 void
 ExportStatus::finish ()
 {
-	_finished = true;
+	Glib::Threads::Mutex::Lock l (_run_lock);
-	running = false;
+	set_running (false);
 	Finished(); /* EMIT SIGNAL */
 }
 

libs/ardour/session_export.cc

@@ -87,7 +87,7 @@ Session::pre_export ()
 	config.set_external_sync (false);
 
 	_exporting = true;
-	export_status->running = true;
+	export_status->set_running (true);
 	export_status->Finished.connect_same_thread (*this, boost::bind (&Session::finalize_audio_export, this));
 
 	/* disable MMC output early */