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feat: unify add/remove commands into queue and fix race on channel removal

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Co-authored-by: aider (deepseek/deepseek-reasoner) <aider@aider.chat>
This commit is contained in:
Loic Coenen
2026-05-09 22:03:11 +00:00
parent a8a9c6164b
commit 437ac31913
4 changed files with 68 additions and 50 deletions
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74
src/looper.c
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@@ -16,16 +16,17 @@
struct channel_t channels[MAX_CHANNELS];
atomic_int channel_count = 0;
int next_channel_id = 1;
atomic_int cmd_add = 0;
atomic_int cmd_remove = 0;
spsc_queue_t cmd_queue_main;
atomic_int global_rt_cycles = 0;
jack_port_t *midi_control_port = NULL;
jack_port_t *midi_clock_port = NULL;
atomic_int control_key_active = 0;
atomic_int bind_channel = 0;
spsc_queue_t cmd_queue;
/* Deferred removal index (1 second grace) */
/* Deferred removal index and cycle counter */
static int pending_unregister_idx = -1;
static int pending_unregister_cycle = 0;
static void apply_command(command_t cmd) {
switch (cmd.type) {
@@ -199,6 +200,7 @@ int process_callback(jack_nframes_t nframes, void *arg) {
}
}
atomic_fetch_add_explicit(&global_rt_cycles, 1, memory_order_release);
return 0;
}
@@ -216,6 +218,7 @@ void jack_shutdown_cb(void *arg) {
* ---------------------------------------------------------------- */
int looper_init(jack_client_t *client) {
queue_init(&cmd_queue);
queue_init(&cmd_queue_main);
/* channel 0 */
channels[0].active = 1;
atomic_store(&channels[0].state, STATE_IDLE);
@@ -250,37 +253,46 @@ int looper_init(jack_client_t *client) {
* main‑loop command processing
* ---------------------------------------------------------------- */
void looper_process_commands(jack_client_t *client) {
/* Unregister any ports that were marked for deferred removal.
By now the real‑time thread has had at least one full cycle
to see the `active = 0` store. */
if (pending_unregister_idx != -1) {
int idx = pending_unregister_idx;
if (channels[idx].audio_in)
jack_port_unregister(client, channels[idx].audio_in);
if (channels[idx].audio_out)
jack_port_unregister(client, channels[idx].audio_out);
pending_unregister_idx = -1;
}
if (atomic_exchange(&cmd_add, 0)) {
int idx;
for (idx = 0; idx < MAX_CHANNELS; idx++)
if (!channels[idx].active)
break;
if (idx < MAX_CHANNELS) {
channel_add(client, idx);
/* Drain main‑loop command queue (add/remove) */
command_t cmd;
while (queue_pop(&cmd_queue_main, &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;
}
}
if (atomic_exchange(&cmd_remove, 0)) {
int remove_idx = -1;
for (int idx = 1; idx < MAX_CHANNELS; idx++)
if (channels[idx].active)
remove_idx = idx;
if (remove_idx != -1) {
/* Mark inactive now; ports will be unregistered next round */
channel_remove(client, remove_idx);
pending_unregister_idx = remove_idx;
/* Deferred port unregistration – wait until RT thread has seen active=0 */
if (pending_unregister_idx != -1) {
int current_cycle = atomic_load(&global_rt_cycles);
if (current_cycle - pending_unregister_cycle >= 1) {
int idx = pending_unregister_idx;
if (channels[idx].audio_in)
jack_port_unregister(client, channels[idx].audio_in);
if (channels[idx].audio_out)
jack_port_unregister(client, channels[idx].audio_out);
pending_unregister_idx = -1;
}
}
}