Merge pull request #4364 from smoogipoo/fix-potential-crossthread

Fix race condition during game load + disposal

osu.Game/OsuGame.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using osu.Framework.Configuration;
 using osu.Framework.Screens;
 using osu.Game.Configuration;
@@ -628,10 +629,24 @@ namespace osu.Game
                     {
                         Logger.Log($"Loading {d}...", level: LogLevel.Debug);
 
+                        // Since this is running in a separate thread, it is possible for OsuGame to be disposed after LoadComponentAsync has been called
+                        // throwing an exception. To avoid this, the call is scheduled on the update thread, which does not run if IsDisposed = true
+                        Task task = null;
+                        var del = new ScheduledDelegate(() => task = LoadComponentAsync(d, add));
+                        Scheduler.Add(del);
+
+                        // The delegate won't complete if OsuGame has been disposed in the meantime
+                        while (!IsDisposed && !del.Completed)
+                            await Task.Delay(10);
+
+                        // Either we're disposed or the load process has started successfully
                         if (IsDisposed)
                             return;
 
-                        await LoadComponentAsync(d, add);
+                        Debug.Assert(task != null);
+
+                        await task;
+
                         Logger.Log($"Loaded {d}!", level: LogLevel.Debug);
                     }
                     catch (OperationCanceledException)