Use a separate backend callback to start playback of the device

This allows us to properly update the ALCdevice and its resources with the new
parameters before starting playback, instead of expecting the mixer to block
and wait after it has begun.

This also lets us avoid holding the device lock while resetting and starting
the device, which helps prevent lock inversion on some backends (ie, one thread
locking A then B, and another thread locking B then A), ultimately allowing
certain backends to asynchronously update the ALCdevice without risk of lockup.
Capture still has issues here, however.

1 files changed, 22 insertions, 19 deletions

diff --git a/Alc/backends/pulseaudio.c b/Alc/backends/pulseaudio.c
index 8fe1118b..78854da7 100644
--- a/Alc/backends/pulseaudio.c
+++ b/Alc/backends/pulseaudio.c
@@ -873,6 +873,10 @@ static void pulse_close(ALCdevice *device)
 
     if(data->stream)
     {
+#if PA_CHECK_VERSION(0,9,15)
+        if(pa_stream_set_buffer_attr_callback)
+            pa_stream_set_buffer_attr_callback(data->stream, NULL, NULL);
+#endif
         pa_stream_disconnect(data->stream);
         pa_stream_unref(data->stream);
     }
@@ -968,6 +972,10 @@ static ALCboolean pulse_reset_playback(ALCdevice *device)
 
     if(data->stream)
     {
+#if PA_CHECK_VERSION(0,9,15)
+        if(pa_stream_set_buffer_attr_callback)
+            pa_stream_set_buffer_attr_callback(data->stream, NULL, NULL);
+#endif
         pa_stream_disconnect(data->stream);
         pa_stream_unref(data->stream);
         data->stream = NULL;
@@ -1079,28 +1087,25 @@ static ALCboolean pulse_reset_playback(ALCdevice *device)
     device->NumUpdates = maxu(device->NumUpdates, 2);
     device->UpdateSize = data->attr.minreq / pa_frame_size(&data->spec);
 
+    pa_threaded_mainloop_unlock(data->loop);
+    return ALC_TRUE;
+}
+
+static ALCboolean pulse_start_playback(ALCdevice *device)
+{
+    pulse_data *data = device->ExtraData;
+
     data->thread = StartThread(PulseProc, device);
     if(!data->thread)
-    {
-#if PA_CHECK_VERSION(0,9,15)
-        if(pa_stream_set_buffer_attr_callback)
-            pa_stream_set_buffer_attr_callback(data->stream, NULL, NULL);
-#endif
-        pa_stream_disconnect(data->stream);
-        pa_stream_unref(data->stream);
-        data->stream = NULL;
-
-        pa_threaded_mainloop_unlock(data->loop);
         return ALC_FALSE;
-    }
 
-    pa_threaded_mainloop_unlock(data->loop);
     return ALC_TRUE;
 }
 
 static void pulse_stop_playback(ALCdevice *device)
 {
     pulse_data *data = device->ExtraData;
+    pa_operation *o;
 
     if(!data->stream)
         return;
@@ -1115,13 +1120,10 @@ static void pulse_stop_playback(ALCdevice *device)
 
     pa_threaded_mainloop_lock(data->loop);
 
-#if PA_CHECK_VERSION(0,9,15)
-    if(pa_stream_set_buffer_attr_callback)
-        pa_stream_set_buffer_attr_callback(data->stream, NULL, NULL);
-#endif
-    pa_stream_disconnect(data->stream);
-    pa_stream_unref(data->stream);
-    data->stream = NULL;
+    o = pa_stream_cork(data->stream, 1, stream_success_callback, device);
+    while(pa_operation_get_state(o) == PA_OPERATION_RUNNING)
+        pa_threaded_mainloop_wait(data->loop);
+    pa_operation_unref(o);
 
     pa_threaded_mainloop_unlock(data->loop);
 }
@@ -1352,6 +1354,7 @@ static const BackendFuncs pulse_funcs = {
     pulse_open_playback,
     pulse_close_playback,
     pulse_reset_playback,
+    pulse_start_playback,
     pulse_stop_playback,
     pulse_open_capture,
     pulse_close_capture,