From b19522c55aa49edecc1e800f1235121bd6682416 Mon Sep 17 00:00:00 2001
From: Paul Giblock <p@pgiblock.net>
Date: Wed, 19 Feb 2014 20:53:50 -0500
Subject: [PATCH] Hopefully fix race-condition in lb302 db24 switch

So, we were swapping out some pointer mid-process at times.  Instead,
use an atomic pointer, and just have the process function grab the
current value and use it through the entire processing period.

Still has a sound glitch when switching, but this switch was never
intended to be used "live".

Closes #353
---
 plugins/lb302/lb302.cpp | 20 ++++++++++----------
 plugins/lb302/lb302.h   |  8 ++++++--
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/plugins/lb302/lb302.cpp b/plugins/lb302/lb302.cpp
index d2dccb93e..7e546cf34 100644
--- a/plugins/lb302/lb302.cpp
+++ b/plugins/lb302/lb302.cpp
@@ -338,7 +338,9 @@ lb302Synth::lb302Synth( InstrumentTrack * _instrumentTrack ) :
 	vca_a = 9;
 	vca_mode = 3;
 
-	vcf = new lb302FilterIIR2(&fs);
+	vcfs[0] = new lb302Filter3Pole(&fs);
+	vcfs[1] = new lb302FilterIIR2(&fs);
+	vcf = vcfs[1];
 
 	sample_cnt = 0;
 	release_frame = 1<<24;
@@ -422,13 +424,8 @@ void lb302Synth::filterChanged()
 
 void lb302Synth::db24Toggled()
 {
-	delete vcf;
-	if(db24Toggle.value()) {
-		vcf = new lb302Filter3Pole(&fs);
-	}
-	else {
-		vcf = new lb302FilterIIR2(&fs);
-	}
+	vcf = vcfs[db24Toggle.value()];
+	// These recalcFilter calls might suck 
 	recalcFilter();
 }
 
@@ -471,6 +468,9 @@ int lb302Synth::process(sampleFrame *outbuf, const int size)
 	float w;
 	float samp;
 
+	// Hold on to the current VCF, and use it throughout this period
+	lb302Filter *filter = vcf;
+
 	if( delete_freq == current_freq ) {
 		// Normal release
 		delete_freq = -1;
@@ -503,7 +503,7 @@ int lb302Synth::process(sampleFrame *outbuf, const int size)
 
 		// update vcf
 		if(vcf_envpos >= ENVINC) {
-			vcf->envRecalc();
+			filter->envRecalc();
 
 			vcf_envpos = 0;
 
@@ -599,7 +599,7 @@ int lb302Synth::process(sampleFrame *outbuf, const int size)
 #ifdef LB_FILTERED
 		//samp = vcf->process(vco_k)*2.0*vca_a;
 		//samp = vcf->process(vco_k)*2.0;
-		samp = vcf->process(vco_k) * vca_a;
+		samp = filter->process(vco_k) * vca_a;
 		//printf("%f %d\n", vco_c, sample_cnt);	
 		
 
diff --git a/plugins/lb302/lb302.h b/plugins/lb302/lb302.h
index 7c6475562..9ce92cfb7 100644
--- a/plugins/lb302/lb302.h
+++ b/plugins/lb302/lb302.h
@@ -39,6 +39,8 @@
 #include "knob.h"
 #include "Mixer.h"
 
+static const int NUM_FILTERS = 2;
+
 class lb302SynthView;
 class NotePlayHandle;
 
@@ -198,13 +200,15 @@ private:
 	enum  vco_shape_t { SAWTOOTH, SQUARE, TRIANGLE, MOOG, ROUND_SQUARE, SINE, EXPONENTIAL, WHITE_NOISE };
 	vco_shape_t vco_shape;
 
+	// Filters (just keep both loaded and switch)
+	lb302Filter* vcfs[NUM_FILTERS];
+
 	// User settings
 	lb302FilterKnobState fs;
-	lb302Filter *vcf;
+	QAtomicPointer<lb302Filter> vcf;
 
 	int release_frame;
 
-
 	// More States
 	int   vcf_envpos;       // Update counter. Updates when >= ENVINC