From ce2dd7be763e8b1d9b7a896dac00fdf05eb0ac9c Mon Sep 17 00:00:00 2001
From: Loic Coenen <loic@visua.com>
Date: Tue, 12 May 2026 19:32:10 +0000
Subject: [PATCH] fix: make channel state variables atomic to eliminate data
 races

Co-authored-by: aider (deepseek/deepseek-reasoner) <aider@aider.chat>
---
 src/channel.h |  6 +++---
 src/looper.c  | 36 ++++++++++++++++++------------------
 2 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/channel.h b/src/channel.h
index 89580bc..d3cd051 100644
--- a/src/channel.h
+++ b/src/channel.h
@@ -19,11 +19,11 @@ typedef enum {
 
 struct channel_t {
     atomic_int    state;
-    int           prev_state;
+    atomic_int    prev_state;
     float         loop_buffer[LOOP_BUF_SIZE];
     atomic_int    loop_count;
-    int           record_pos;
-    int           playback_pos;
+    atomic_int    record_pos;
+    atomic_int    playback_pos;
     atomic_int    active;
     jack_port_t  *audio_in;
     jack_port_t  *audio_out;
diff --git a/src/looper.c b/src/looper.c
index cbffec6..c80ca27 100644
--- a/src/looper.c
+++ b/src/looper.c
@@ -68,16 +68,16 @@ int process_callback(jack_nframes_t nframes, void *arg) {
 
     int state = atomic_load(&channels[c].state);
 
-    if (state != channels[c].prev_state) {
+    if (state != atomic_load(&channels[c].prev_state)) {
       switch (state) {
       case STATE_RECORD:
-        channels[c].record_pos = 0;
+        atomic_store(&channels[c].record_pos, 0);
         atomic_store(&channels[c].loop_count, 0);
         break;
       case STATE_LOOPING:
-        if (channels[c].prev_state == STATE_RECORD && channels[c].record_pos > 0)
-          atomic_store(&channels[c].loop_count, channels[c].record_pos);
-        channels[c].playback_pos = 0;
+        if (atomic_load(&channels[c].prev_state) == STATE_RECORD && atomic_load(&channels[c].record_pos) > 0)
+          atomic_store(&channels[c].loop_count, atomic_load(&channels[c].record_pos));
+        atomic_store(&channels[c].playback_pos, 0);
         break;
       default:
         break;
@@ -91,9 +91,9 @@ int process_callback(jack_nframes_t nframes, void *arg) {
         float *f_out = (float *)out;
         const float *f_in = (const float *)in;
         for (i = 0; i < nframes; i++) {
-          if (channels[c].record_pos < LOOP_BUF_SIZE)
-            channels[c].loop_buffer[channels[c].record_pos++] =
-                f_in[i];
+          int rp = atomic_fetch_add(&channels[c].record_pos, 1);
+          if (rp < LOOP_BUF_SIZE)
+            channels[c].loop_buffer[rp] = f_in[i];
           f_out[i] = f_in[i];
         }
       } else {
@@ -106,9 +106,9 @@ int process_callback(jack_nframes_t nframes, void *arg) {
       if (lc > 0) {
         float *outf = (float *)out;
         for (i = 0; i < nframes; i++) {
-          outf[i] = channels[c].loop_buffer[channels[c].playback_pos];
-          channels[c].playback_pos =
-              (channels[c].playback_pos + 1) % lc;
+          int pp = atomic_load(&channels[c].playback_pos);
+          outf[i] = channels[c].loop_buffer[pp];
+          atomic_store(&channels[c].playback_pos, (pp + 1) % lc);
         }
       } else {
         memset(out, 0, sizeof(jack_default_audio_sample_t) * nframes);
@@ -137,7 +137,7 @@ int process_callback(jack_nframes_t nframes, void *arg) {
       }
     }
 
-    channels[c].prev_state = state;
+    atomic_store(&channels[c].prev_state, state);
   }
 
   /* MIDI clock events – affect channel 0 only */
@@ -197,10 +197,10 @@ int looper_init(jack_client_t *client) {
   /* channel 0 */
   channels[0].active = 1;
   atomic_store(&channels[0].state, STATE_IDLE);
-  channels[0].prev_state = -1;
+  atomic_store(&channels[0].prev_state, -1);
   channels[0].loop_count = 0;
-  channels[0].record_pos = 0;
-  channels[0].playback_pos = 0;
+  atomic_store(&channels[0].record_pos, 0);
+  atomic_store(&channels[0].playback_pos, 0);
   atomic_store_explicit(&channels[0].save_ring, NULL, memory_order_release);
 
   channels[0].audio_in = jack_port_register(
@@ -312,10 +312,10 @@ void looper_process_commands(jack_client_t *client) {
       if (frames > LOOP_BUF_SIZE) frames = LOOP_BUF_SIZE;
       memcpy(channels[0].loop_buffer, buf, frames * sizeof(float));
       atomic_store(&channels[0].loop_count, (int)frames);
-      channels[0].record_pos  = 0;
-      channels[0].playback_pos = 0;
+      atomic_store(&channels[0].record_pos, 0);
+      atomic_store(&channels[0].playback_pos, 0);
       atomic_store(&channels[0].state, STATE_LOOPING);
-      channels[0].prev_state = -1;
+      atomic_store(&channels[0].prev_state, -1);
       free(buf);
     } else {
       fprintf(stderr, "Failed to load loop.wav\n");