Add a waiting state

Also fix erroneous looking switch fall-through.

Author: cwoffenden

test/webaudio/audioworklet_emscripten_locks.c

@@ -17,6 +17,8 @@
 int _emscripten_thread_supports_atomics_wait(void);
 
 typedef enum {
+  // The test hasn't yet started
+  TEST_NOT_STARTED,
   // No wait support in audio worklets
   TEST_HAS_WAIT,
   // Acquired in main, fail in process
@@ -40,26 +42,17 @@ typedef enum {
 // Lock used in all the tests
 emscripten_lock_t testLock = EMSCRIPTEN_LOCK_T_STATIC_INITIALIZER;
 // Which test is running (sometimes in the worklet, sometimes in the main thread)
-_Atomic Test whichTest = TEST_HAS_WAIT;
+_Atomic Test whichTest = TEST_NOT_STARTED;
 // Time at which the test starts taken in main()
 double startTime = 0;
 
 bool ProcessAudio(int numInputs, const AudioSampleFrame *inputs, int numOutputs, AudioSampleFrame *outputs, int numParams, const AudioParamFrame *params, void *userData) {
   assert(emscripten_current_thread_is_audio_worklet());
 
-  // Produce at few empty frames of audio before we start trying to interact
-  // with the with main thread.
-  // On chrome at least it appears the main thread completely blocks until
-  // a few frames have been produced.  This means it may not be safe to interact
-  // with the main thread during initial frames?
-  // In my experiments it seems like 5 was the magic number that I needed to
-  // produce before the main thread could continue to run.
-  // See https://github.com/emscripten-core/emscripten/issues/24213
-  static int count = 0;
-  if (count++ < 5) return true;
-
   int result = 0;
   switch (whichTest) {
+  case TEST_NOT_STARTED:
+    break;
   case TEST_HAS_WAIT:
     // Should not have wait support here
     result = _emscripten_thread_supports_atomics_wait();
@@ -80,6 +73,7 @@ bool ProcessAudio(int numInputs, const AudioSampleFrame *inputs, int numOutputs,
     emscripten_outf("TEST_WAIT_ACQUIRE_FAIL: %d (expect: 0)", result);
     assert(!result);
     whichTest = TEST_WAIT_ACQUIRE;
+    break;
   case TEST_WAIT_ACQUIRE:
     // Will get unlocked in main thread, so should quickly acquire
     result = emscripten_lock_busyspin_wait_acquire(&testLock, 10000);
@@ -130,6 +124,10 @@ bool MainLoop(double time, void* data) {
   assert(!emscripten_current_thread_is_audio_worklet());
   static int didUnlock = false;
   switch (whichTest) {
+  case TEST_NOT_STARTED:
+    emscripten_out("Staring test (may need a button click)");
+    whichTest = TEST_HAS_WAIT;
+    break;
   case TEST_WAIT_ACQUIRE:
     if (!didUnlock) {
       emscripten_out("main thread releasing lock");
@@ -178,9 +176,9 @@ int main() {
 
   startTime = emscripten_get_now();
 
-  emscripten_set_timeout_loop(MainLoop, 10, NULL);
   EMSCRIPTEN_WEBAUDIO_T context = emscripten_create_audio_context(NULL);
   emscripten_start_wasm_audio_worklet_thread_async(context, wasmAudioWorkletStack, sizeof(wasmAudioWorkletStack), WebAudioWorkletThreadInitialized, NULL);
+  emscripten_set_timeout_loop(MainLoop, 10, NULL);
 
   emscripten_exit_with_live_runtime();
 }