Don't fill backend info when core is running

The current approach results in the UI thread creating a graphics device
whilst the core is running, leading to races on function pointers, and
potentially crashing.

Source/Core/DolphinQt/Config/Graphics/GraphicsWindow.cpp

@@ -38,9 +38,6 @@ void GraphicsWindow::Initialize()
 
   m_lazy_initialized = true;
 
-  g_Config.Refresh();
-  g_video_backend->InitBackendInfo();
-
   CreateMainLayout();
 
   setWindowTitle(tr("Graphics"));
@@ -109,18 +106,7 @@ void GraphicsWindow::CreateMainLayout()
 void GraphicsWindow::OnBackendChanged(const QString& backend_name)
 {
   SConfig::GetInstance().m_strVideoBackend = backend_name.toStdString();
-
-  for (const auto& backend : g_available_video_backends)
-  {
-    if (backend->GetName() == backend_name.toStdString())
-    {
-      g_Config.Refresh();
-
-      g_video_backend = backend.get();
-      g_video_backend->InitBackendInfo();
-      break;
-    }
-  }
+  VideoBackendBase::PopulateBackendInfo();
 
   setWindowTitle(
       tr("%1 Graphics Configuration").arg(tr(g_video_backend->GetDisplayName().c_str())));

Source/Core/VideoCommon/VideoBackendBase.cpp

@@ -14,6 +14,8 @@
 #include "Common/CommonTypes.h"
 #include "Common/Event.h"
 #include "Common/Logging/Log.h"
+#include "Core/ConfigManager.h"
+#include "Core/Core.h"
 #include "Core/Host.h"
 
 // TODO: ugly
@@ -223,6 +225,20 @@ void VideoBackendBase::ActivateBackend(const std::string& name)
   g_video_backend = iter->get();
 }
 
+void VideoBackendBase::PopulateBackendInfo()
+{
+  // If the core is running, the backend info will have been populated already.
+  // If we did it here, the UI thread can race with the with the GPU thread.
+  if (Core::IsRunning())
+    return;
+
+  // We refresh the config after initializing the backend info, as system-specific settings
+  // such as anti-aliasing, or the selected adapter may be invalid, and should be checked.
+  ActivateBackend(SConfig::GetInstance().m_strVideoBackend);
+  g_video_backend->InitBackendInfo();
+  g_Config.Refresh();
+}
+
 // Run from the CPU thread
 void VideoBackendBase::DoState(PointerWrap& p)
 {

Source/Core/VideoCommon/VideoBackendBase.h

@@ -54,6 +54,10 @@ public:
   static void ClearList();
   static void ActivateBackend(const std::string& name);
 
+  // Fills the backend_info fields with the capabilities of the selected backend/device.
+  // Called by the UI thread when the graphics config is opened.
+  static void PopulateBackendInfo();
+
   // the implementation needs not do synchronization logic, because calls to it are surrounded by
   // PauseAndLock now
   void DoState(PointerWrap& p);