changed busy flag into busy mutex, improves thread safety

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@352 0778d3d1-df1d-0410-868b-ea421aaaa00d

include/envelope_and_lfo_widget.h

@@ -89,7 +89,7 @@ public:
 
 	float FASTCALL level( f_cnt_t _frame,
 				const f_cnt_t _release_begin,
-				const f_cnt_t _frame_offset ) const;
+				const f_cnt_t _frame_offset );
 
 	inline bool used( void ) const
 	{
@@ -105,6 +105,15 @@ public:
 		return( "el" );
 	}
 
+	void lock( void )
+	{
+		m_busyMutex.lock();
+	}
+	void unlock( void )
+	{
+		m_busyMutex.unlock();
+	}
+
 
 public slots:
 	void updateSampleVars( void );
@@ -183,7 +192,7 @@ private:
 		USER
 	} m_lfoShape;
 
-	volatile bool m_busy;
+	QMutex m_busyMutex;