Expedite discovery of primary DRM device.

ui/ozone/platform/drm/host/drm_gpu_platform_support_host.cc

Index: ui/ozone/platform/drm/host/drm_gpu_platform_support_host.cc
diff --git a/ui/ozone/platform/drm/host/drm_gpu_platform_support_host.cc b/ui/ozone/platform/drm/host/drm_gpu_platform_support_host.cc
index 75096a0cb8dc615b89ceed60ffcd6e0642afc774..9021440d34598e37529f89b1b495f5709ea8d48e 100644
--- a/ui/ozone/platform/drm/host/drm_gpu_platform_support_host.cc
+++ b/ui/ozone/platform/drm/host/drm_gpu_platform_support_host.cc
@@ -103,17 +103,24 @@ bool DrmGpuPlatformSupportHost::IsConnected() {
   return host_id_ >= 0;
 }
 
-void DrmGpuPlatformSupportHost::OnChannelEstablished(
+void DrmGpuPlatformSupportHost::OnGpuProcessLaunched(
     int host_id,
     scoped_refptr<base::SingleThreadTaskRunner> send_runner,
     const base::Callback<void(IPC::Message*)>& send_callback) {
-  TRACE_EVENT1("drm", "DrmGpuPlatformSupportHost::OnChannelEstablished",
+  TRACE_EVENT1("drm", "DrmGpuPlatformSupportHost::OnGpuProcessLaunched",
                "host_id", host_id);
   host_id_ = host_id;

[dnicoara, 2016/10/28 21:42:54]

One of the odd things about GpuProcessHost[UIShim] is that OnChannelDestroyed()
may be called after the new GPU process is launched. So you can't update these
on IO without some kind of locking.

[dnicoara, 2016/10/31 22:01:25]

Setting the |host_id_|, |send_runner_| and |send_callback_| from IO is causing
your issues. What you want to do is to make sure these are only set from the UI
process.

As a first pass I'd suggest passing in |send_callback_| to
|observer.OnGpuProcessLaunched()|. That way DrmDisplayHostManager may call the
callback directly. This will need to change to accommodate for MUS code, but at
least will get you a step closer.

 

   send_runner_ = send_runner;
   send_callback_ = send_callback;
 
   for (GpuThreadObserver& observer : gpu_thread_observers_)

[dnicoara, 2016/10/28 21:42:54]

This is another place where the observer vector is accessed from multiple
threads. It could be problematic.

+    observer.OnGpuProcessLaunched();
+}
+
+void DrmGpuPlatformSupportHost::OnChannelEstablished() {
+  TRACE_EVENT0("drm", "DrmGpuPlatformSupportHost::OnChannelEstablished");
+
+  for (GpuThreadObserver& observer : gpu_thread_observers_)
     observer.OnGpuThreadReady();
 
   // The cursor is special since it will process input events on the IO thread