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, 11 insertions, 3 deletions

diff --git a/Alc/backends/oss.c b/Alc/backends/oss.c
index bd489e3e..a577d8be 100644
--- a/Alc/backends/oss.c
+++ b/Alc/backends/oss.c
@@ -268,11 +268,18 @@ static ALCboolean oss_reset_playback(ALCdevice *device)
     device->UpdateSize = info.fragsize / frameSize;
     device->NumUpdates = info.fragments + 1;
 
-    data->data_size = device->UpdateSize * frameSize;
-    data->mix_data = calloc(1, data->data_size);
-
     SetDefaultChannelOrder(device);
 
+    return ALC_TRUE;
+}
+
+static ALCboolean oss_start_playback(ALCdevice *device)
+{
+    oss_data *data = (oss_data*)device->ExtraData;
+
+    data->data_size = device->UpdateSize * FrameSizeFromDevFmt(device->FmtChans, device->FmtType);
+    data->mix_data = calloc(1, data->data_size);
+
     data->thread = StartThread(OSSProc, device);
     if(data->thread == NULL)
     {
@@ -473,6 +480,7 @@ static const BackendFuncs oss_funcs = {
     oss_open_playback,
     oss_close_playback,
     oss_reset_playback,
+    oss_start_playback,
     oss_stop_playback,
     oss_open_capture,
     oss_close_capture,