Expedite discovery of primary DRM device.

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/ozone/platform/drm/host/drm_display_host_manager.h"
 
 #include <fcntl.h>
 #include <stddef.h>
 #include <xf86drm.h>
 
@@ skipping 288 matching lines @@
 }
 
 void DrmDisplayHostManager::OnRemoveGraphicsDevice(
     const base::FilePath& sys_path) {
   proxy_->GpuRemoveGraphicsDevice(sys_path);
   NotifyDisplayDelegate();
   task_pending_ = false;
   ProcessEvent();
 }
 
-void DrmDisplayHostManager::OnGpuThreadReady() {
-  // If in the middle of a configuration, just respond with the old list of
-  // displays. This is fine, since after the DRM resources are initialized and
-  // IPC-ed to the GPU NotifyDisplayDelegate() is called to let the display
-  // delegate know that the display configuration changed and it needs to
-  // update it again.
-  if (!get_displays_callback_.is_null()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
-        FROM_HERE,
-        base::Bind(&DrmDisplayHostManager::RunUpdateDisplaysCallback,
-                   weak_ptr_factory_.GetWeakPtr(), get_displays_callback_));
-    get_displays_callback_.Reset();
-  }
-
-  // Signal that we're taking DRM master since we're going through the
-  // initialization process again and we'll take all the available resources.
-  if (!take_display_control_callback_.is_null())
-    GpuTookDisplayControl(true);
-
-  if (!relinquish_display_control_callback_.is_null())
-    GpuRelinquishedDisplayControl(false);
-
+void DrmDisplayHostManager::OnGpuProcessLaunched() {
   std::unique_ptr<DrmDeviceHandle> handle =
       std::move(primary_drm_device_handle_);
   {
     base::ThreadRestrictions::ScopedAllowIO allow_io;
 
     drm_devices_.clear();
     drm_devices_[primary_graphics_card_path_] =

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

|drm_devices_| can't be accessed on multiple threads. This is likely one place
you might get exceptions from.

         MapDevPathToSysPath(primary_graphics_card_path_);
 
     if (!handle) {
       handle.reset(new DrmDeviceHandle());
       if (!handle->Initialize(primary_graphics_card_path_,
                               drm_devices_[primary_graphics_card_path_]))
         LOG(FATAL) << "Failed to open primary graphics card";
     }
   }
 
   // Send the primary device first since this is used to initialize graphics
   // state.
   proxy_->GpuAddGraphicsDevice(drm_devices_[primary_graphics_card_path_],

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

You may need to check how the buffer allocation is posted, but be aware that
|proxy_| will post a task to the IO task runner. You may need something better
to just invoke the Send() callback rather than posting it.

                                base::FileDescriptor(handle->PassFD()));
+}
+
+void DrmDisplayHostManager::OnGpuThreadReady() {
+  // If in the middle of a configuration, just respond with the old list of
+  // displays. This is fine, since after the DRM resources are initialized and
+  // IPC-ed to the GPU NotifyDisplayDelegate() is called to let the display
+  // delegate know that the display configuration changed and it needs to
+  // update it again.
+  if (!get_displays_callback_.is_null()) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE,
+        base::Bind(&DrmDisplayHostManager::RunUpdateDisplaysCallback,
+                   weak_ptr_factory_.GetWeakPtr(), get_displays_callback_));
+    get_displays_callback_.Reset();
+  }
+
+  // Signal that we're taking DRM master since we're going through the
+  // initialization process again and we'll take all the available resources.
+  if (!take_display_control_callback_.is_null())
+    GpuTookDisplayControl(true);
+
+  if (!relinquish_display_control_callback_.is_null())
+    GpuRelinquishedDisplayControl(false);
 
   device_manager_->ScanDevices(this);
   NotifyDisplayDelegate();
 }
 
 void DrmDisplayHostManager::OnGpuThreadRetired() {}
 
 void DrmDisplayHostManager::GpuHasUpdatedNativeDisplays(
     const std::vector<DisplaySnapshot_Params>& params) {
   std::vector<std::unique_ptr<DrmDisplayHost>> old_displays;
@@ skipping 96 matching lines @@
 
   callback.Run(snapshots);
 }
 
 void DrmDisplayHostManager::NotifyDisplayDelegate() const {
   if (delegate_)
     delegate_->OnConfigurationChanged();
 }
 
 }  // namespace ui