fix: split main command queue into per-source SPSC queues

Co-authored-by: aider (deepseek/deepseek-reasoner) <aider@aider.chat>

src/looper.c

@@ -16,7 +16,8 @@
 struct channel_t channels[MAX_CHANNELS];
 atomic_int channel_count = 0;
 int next_channel_id = 1;
-spsc_queue_t cmd_queue_main;
+spsc_queue_t cmd_queue_main_midi;
+spsc_queue_t cmd_queue_main_fifo;
 atomic_int global_rt_cycles = 0;
 jack_port_t *midi_control_port = NULL;
 jack_port_t *midi_clock_port = NULL;
@@ -218,7 +219,8 @@ void jack_shutdown_cb(void *arg) {
  * ---------------------------------------------------------------- */
 int looper_init(jack_client_t *client) {
   queue_init(&cmd_queue);
-  queue_init(&cmd_queue_main);
+  queue_init(&cmd_queue_main_midi);
+  queue_init(&cmd_queue_main_fifo);
   /* channel 0 */
   channels[0].active = 1;
   atomic_store(&channels[0].state, STATE_IDLE);
@@ -253,9 +255,36 @@ int looper_init(jack_client_t *client) {
  * main‑loop command processing
  * ---------------------------------------------------------------- */
 void looper_process_commands(jack_client_t *client) {
-  /* Drain main‑loop command queue (add/remove) */
+  /* Drain main‑loop command queues (add/remove) */
   command_t cmd;
-  while (queue_pop(&cmd_queue_main, &cmd)) {
+  while (queue_pop(&cmd_queue_main_midi, &cmd)) {
+    switch (cmd.type) {
+    case CMD_ADD_CHANNEL: {
+      int idx;
+      for (idx = 0; idx < MAX_CHANNELS; idx++)
+        if (!channels[idx].active)
+          break;
+      if (idx < MAX_CHANNELS)
+        channel_add(client, idx);
+      break;
+    }
+    case CMD_REMOVE_CHANNEL: {
+      int remove_idx = -1;
+      for (int idx = 1; idx < MAX_CHANNELS; idx++)
+        if (channels[idx].active)
+          remove_idx = idx;
+      if (remove_idx != -1) {
+        channel_remove(client, remove_idx);
+        pending_unregister_idx = remove_idx;
+        pending_unregister_cycle = atomic_load(&global_rt_cycles);
+      }
+      break;
+    }
+    default:
+      break;
+    }
+  }
+  while (queue_pop(&cmd_queue_main_fifo, &cmd)) {
     switch (cmd.type) {
     case CMD_ADD_CHANNEL: {
       int idx;

src/midi.c

@@ -10,7 +10,7 @@
 extern atomic_int control_key_active;
 extern atomic_int bind_channel;
 extern spsc_queue_t cmd_queue;
-extern spsc_queue_t cmd_queue_main;
+extern spsc_queue_t cmd_queue_main_midi;
 
 void midi_handle_events(void *port_buffer, jack_nframes_t nframes) {
   (void)nframes;
@@ -40,10 +40,16 @@ void midi_handle_events(void *port_buffer, jack_nframes_t nframes) {
             queue_push(&cmd_queue, cmd);
           } else {
             switch (note) {
-            case 60: /* add channel not rt‑safe, moved to FIFO pipe */
+            case 60:
-            case 61: /* remove channel not rt‑safe, moved to FIFO pipe */
+            {
-              /* no operation here */
+              command_t cmd = { .type = CMD_ADD_CHANNEL, .channel = -1, .data = 0 };
-              break;
+              queue_push(&cmd_queue_main_midi, cmd);
+            } break;
+            case 61:
+            {
+              command_t cmd = { .type = CMD_REMOVE_CHANNEL, .channel = -1, .data = 0 };
+              queue_push(&cmd_queue_main_midi, cmd);
+            } break;
             case 62:
             {
               int bch = atomic_load(&bind_channel);
@@ -69,10 +75,16 @@ void midi_handle_events(void *port_buffer, jack_nframes_t nframes) {
               command_t cmd = { .type = CMD_CYCLE, .channel = 0, .data = 0 };
               queue_push(&cmd_queue, cmd);
             } break;
-          case 60: /* add channel not rt‑safe, moved to FIFO pipe */
+          case 60:
-          case 61: /* remove channel not rt‑safe, moved to FIFO pipe */
+          {
-            /* no operation here */
+            command_t cmd = { .type = CMD_ADD_CHANNEL, .channel = -1, .data = 0 };
-            break;
+            queue_push(&cmd_queue_main_midi, cmd);
+          } break;
+          case 61:
+          {
+            command_t cmd = { .type = CMD_REMOVE_CHANNEL, .channel = -1, .data = 0 };
+            queue_push(&cmd_queue_main_midi, cmd);
+          } break;
           default:
             break;
           }

src/pipe.c

@@ -15,7 +15,7 @@
 
 /* forward‑declare the global queues (defined in looper.c) */
 extern spsc_queue_t cmd_queue;
-extern spsc_queue_t cmd_queue_main;
+extern spsc_queue_t cmd_queue_main_fifo;
 
 static void *pipe_thread_func(void *arg) {
     (void)arg;
@@ -33,10 +33,10 @@ static void *pipe_thread_func(void *arg) {
 
         if (strcmp(line, "add") == 0) {
             command_t cmd = { .type = CMD_ADD_CHANNEL, .channel = -1, .data = 0 };
-            queue_push(&cmd_queue_main, cmd);
+            queue_push(&cmd_queue_main_fifo, cmd);
         } else if (strcmp(line, "remove") == 0) {
             command_t cmd = { .type = CMD_REMOVE_CHANNEL, .channel = -1, .data = 0 };
-            queue_push(&cmd_queue_main, cmd);
+            queue_push(&cmd_queue_main_fifo, cmd);
         } else if (strncmp(line, "record ", 7) == 0) {
             int ch = atoi(line + 7);
             command_t cmd = { .type = CMD_CYCLE, .channel = ch, .data = 0 };