Prevent crash in pool destruction during session teardown.

git-svn-id: svn://localhost/ardour2/branches/3.0@6905 d708f5d6-7413-0410-9779-e7cbd77b26cf

libs/ardour/ardour/butler.h

@@ -49,6 +49,7 @@ class Butler : public SessionHandleRef
 	void stop();
 	void wait_until_finished();
 	bool transport_work_requested() const;
+	void drop_references ();
 
 	float read_data_rate() const; ///< in usec
 	float write_data_rate() const;

libs/ardour/butler.cc

@@ -428,5 +428,12 @@ Butler::empty_pool_trash ()
 	}
 }
 
+void
+Butler::drop_references ()
+{
+	SessionEvent::pool->set_trash (0);
+}
+
+
 } // namespace ARDOUR
 

libs/ardour/session.cc

@@ -229,6 +229,7 @@ Session::destroy ()
 
 	Stateful::loading_state_version = 0;
 
+	_butler->drop_references ();
 	delete _butler;
 	delete midi_control_ui;
 

libs/pbd/pbd/pool.h

@@ -111,10 +111,7 @@ class PerThreadPool
 	void  create_per_thread_pool (std::string name, unsigned long item_size, unsigned long nitems);
 	CrossThreadPool* per_thread_pool ();
 
-	void set_trash (RingBuffer<CrossThreadPool*>* t) {
-		_trash = t;
-	}
-
+	void set_trash (RingBuffer<CrossThreadPool*>* t);
 	void add_to_trash (CrossThreadPool *);
 
   private:
@@ -122,8 +119,10 @@ class PerThreadPool
 	std::string _name;
 	unsigned long _item_size;
 	unsigned long _nitems;
+
+	/** mutex to protect either changes to the _trash variable, or writes to the RingBuffer */
+	Glib::Mutex _trash_mutex;
 	RingBuffer<CrossThreadPool*>* _trash;
-	Glib::Mutex _trash_write_mutex;
 };
 
 #endif // __qm_pool_h__

libs/pbd/pool.cc

@@ -198,10 +198,19 @@ PerThreadPool::per_thread_pool ()
 	return p;
 }
 
+void
+PerThreadPool::set_trash (RingBuffer<CrossThreadPool*>* t)
+{
+	Glib::Mutex::Lock lm (_trash_mutex);
+	_trash = t;
+}
+
 /** Add a CrossThreadPool to our trash, if we have one.  If not, a warning is emitted. */
 void
 PerThreadPool::add_to_trash (CrossThreadPool* p)
 {
+	Glib::Mutex::Lock lm (_trash_mutex);
+	
 	if (!_trash) {
 		warning << "Pool " << p->name() << " has no trash collector; a memory leak has therefore occurred" << endmsg;
 		return;
@@ -211,7 +220,6 @@ PerThreadPool::add_to_trash (CrossThreadPool* p)
 	   can only be one writer to the _trash RingBuffer)
 	*/
 		
-	Glib::Mutex::Lock lm (_trash_write_mutex);
 	_trash->write (&p, 1);
 }