lock user waveform once per loop

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@317 0778d3d1-df1d-0410-868b-ea421aaaa00d

src/lib/oscillator.cpp

@@ -55,6 +55,8 @@ oscillator::oscillator( const waveShapes * _wave_shape,
 void oscillator::update( sampleFrame * _ab, const fpab_t _frames,
 							const ch_cnt_t _chnl )
 {
+	m_userWave->lock();
+
 	if( m_subOsc != NULL )
 	{
 		switch( *m_modulationAlgo )
@@ -79,6 +81,8 @@ void oscillator::update( sampleFrame * _ab, const fpab_t _frames,
 	{
 		updateNoSub( _ab, _frames, _chnl );
 	}
+
+	m_userWave->unlock();
 }