From 791c2c716d7fbf2e63964ebfdcd331bcefea643d Mon Sep 17 00:00:00 2001
From: Jan Svabenik <jan@svabi.ch>
Date: Thu, 19 Mar 2026 14:15:14 +0100
Subject: [PATCH] Use synchronized GPU engine access in recorder demod paths

---
 internal/recorder/demod.go      | 11 ++++++-----
 internal/recorder/demod_live.go |  7 ++++---
 internal/recorder/recorder.go   |  6 ++++++
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/internal/recorder/demod.go b/internal/recorder/demod.go
index 57253ff..23741af 100644
--- a/internal/recorder/demod.go
+++ b/internal/recorder/demod.go
@@ -29,7 +29,8 @@ func (m *Manager) demodAndWrite(dir string, ev detector.Event, iq []complex64, f
 	offset := ev.CenterHz - m.centerHz
 	var audio []float32
 	var inputRate int
-	if m.gpuDemod != nil {
+	gpu := m.gpuEngine()
+	if gpu != nil {
 		var gpuMode gpudemod.DemodType
 		var useGPU bool
 		switch name {
@@ -47,18 +48,18 @@ func (m *Manager) demodAndWrite(dir string, ev detector.Event, iq []complex64, f
 			gpuMode, useGPU = gpudemod.DemodCW, true
 		}
 		if useGPU {
-			if gpuAudio, gpuRate, err := m.gpuDemod.DemodFused(iq, offset, bw, gpuMode); err == nil {
+			if gpuAudio, gpuRate, err := gpu.DemodFused(iq, offset, bw, gpuMode); err == nil {
 				audio = gpuAudio
 				inputRate = gpuRate
-				if m.gpuDemod.LastDemodUsedGPU() {
+				if gpu.LastDemodUsedGPU() {
 					log.Printf("gpudemod: fused GPU demod used for event %d (%s)", ev.ID, name)
 				}
 			} else {
 				log.Printf("gpudemod: fused GPU demod failed for event %d (%s): %v", ev.ID, name, err)
-				if gpuAudio, gpuRate, err := m.gpuDemod.Demod(iq, offset, bw, gpuMode); err == nil {
+				if gpuAudio, gpuRate, err := gpu.Demod(iq, offset, bw, gpuMode); err == nil {
 					audio = gpuAudio
 					inputRate = gpuRate
-					if m.gpuDemod.LastDemodUsedGPU() {
+					if gpu.LastDemodUsedGPU() {
 						log.Printf("gpudemod: legacy GPU demod used for event %d (%s)", ev.ID, name)
 					}
 				} else {
diff --git a/internal/recorder/demod_live.go b/internal/recorder/demod_live.go
index 0c473c0..d27ef3c 100644
--- a/internal/recorder/demod_live.go
+++ b/internal/recorder/demod_live.go
@@ -46,7 +46,8 @@ func (m *Manager) DemodLive(centerHz float64, bw float64, mode string, seconds i
 
 	var audio []float32
 	var inputRate int
-	if m.gpuDemod != nil {
+	gpu := m.gpuEngine()
+	if gpu != nil {
 		var gpuMode gpudemod.DemodType
 		var useGPU bool
 		switch name {
@@ -64,13 +65,13 @@ func (m *Manager) DemodLive(centerHz float64, bw float64, mode string, seconds i
 			gpuMode, useGPU = gpudemod.DemodCW, true
 		}
 		if useGPU {
-			if gpuAudio, gpuRate, err := m.gpuDemod.DemodFused(segment, offset, bw, gpuMode); err == nil {
+			if gpuAudio, gpuRate, err := gpu.DemodFused(segment, offset, bw, gpuMode); err == nil {
 				audio = gpuAudio
 				inputRate = gpuRate
 				log.Printf("gpudemod: fused GPU live demod used (%s)", name)
 			} else {
 				log.Printf("gpudemod: fused GPU live demod failed (%s): %v", name, err)
-				if gpuAudio, gpuRate, err := m.gpuDemod.Demod(segment, offset, bw, gpuMode); err == nil {
+				if gpuAudio, gpuRate, err := gpu.Demod(segment, offset, bw, gpuMode); err == nil {
 					audio = gpuAudio
 					inputRate = gpuRate
 					log.Printf("gpudemod: legacy GPU live demod used (%s)", name)
diff --git a/internal/recorder/recorder.go b/internal/recorder/recorder.go
index 6c77ef7..88a7298 100644
--- a/internal/recorder/recorder.go
+++ b/internal/recorder/recorder.go
@@ -120,6 +120,12 @@ func (m *Manager) initGPUDemod(sampleRate int, blockSize int) {
 	m.initGPUDemodLocked(sampleRate, blockSize)
 }
 
+func (m *Manager) gpuEngine() *gpudemod.Engine {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	return m.gpuDemod
+}
+
 func (m *Manager) initGPUDemodLocked(sampleRate int, blockSize int) {
 	if m.gpuDemod != nil {
 		m.gpuDemod.Close()