From ad3a01dc06215e17458357189cac15b9c603d093 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Fri, 21 Jan 2022 22:40:18 +0900
Subject: [PATCH] Use a more reliable method of reviving the update thread
 realm after blocking

---
 osu.Game/Database/RealmContextFactory.cs      | 44 +++++++++++--------
 .../Sections/DebugSettings/MemorySettings.cs  |  4 --
 2 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/osu.Game/Database/RealmContextFactory.cs b/osu.Game/Database/RealmContextFactory.cs
index d9c66ccc69..6fb9a2996b 100644
--- a/osu.Game/Database/RealmContextFactory.cs
+++ b/osu.Game/Database/RealmContextFactory.cs
@@ -69,30 +69,29 @@ namespace osu.Game.Database
 
         private Realm? context;
 
-        public Realm Context
+        public Realm Context => ensureUpdateContext();
+
+        private Realm ensureUpdateContext()
         {
-            get
+            if (!ThreadSafety.IsUpdateThread)
+                throw new InvalidOperationException(@$"Use {nameof(createContext)} when performing realm operations from a non-update thread");
+
+            lock (contextLock)
             {
-                if (!ThreadSafety.IsUpdateThread)
-                    throw new InvalidOperationException(@$"Use {nameof(createContext)} when performing realm operations from a non-update thread");
-
-                lock (contextLock)
+                if (context == null)
                 {
-                    if (context == null)
-                    {
-                        context = createContext();
-                        Logger.Log(@$"Opened realm ""{context.Config.DatabasePath}"" at version {context.Config.SchemaVersion}");
+                    context = createContext();
+                    Logger.Log(@$"Opened realm ""{context.Config.DatabasePath}"" at version {context.Config.SchemaVersion}");
 
-                        // Resubscribe any subscriptions
-                        foreach (var action in subscriptionActions.Keys)
-                            registerSubscription(action);
-                    }
-
-                    Debug.Assert(context != null);
-
-                    // creating a context will ensure our schema is up-to-date and migrated.
-                    return context;
+                    // Resubscribe any subscriptions
+                    foreach (var action in subscriptionActions.Keys)
+                        registerSubscription(action);
                 }
+
+                Debug.Assert(context != null);
+
+                // creating a context will ensure our schema is up-to-date and migrated.
+                return context;
             }
         }
 
@@ -506,6 +505,8 @@ namespace osu.Game.Database
             if (isDisposed)
                 throw new ObjectDisposedException(nameof(RealmContextFactory));
 
+            SynchronizationContext syncContext;
+
             try
             {
                 contextCreationLock.Wait();
@@ -515,6 +516,8 @@ namespace osu.Game.Database
                     if (!ThreadSafety.IsUpdateThread && context != null)
                         throw new InvalidOperationException(@$"{nameof(BlockAllOperations)} must be called from the update thread.");
 
+                    syncContext = SynchronizationContext.Current;
+
                     Logger.Log(@"Blocking realm operations.", LoggingTarget.Database);
 
                     context?.Dispose();
@@ -553,6 +556,9 @@ namespace osu.Game.Database
             {
                 factory.contextCreationLock.Release();
                 Logger.Log(@"Restoring realm operations.", LoggingTarget.Database);
+
+                // Post back to the update thread to revive any subscriptions.
+                syncContext?.Post(_ => ensureUpdateContext(), null);
             });
         }
 
diff --git a/osu.Game/Overlays/Settings/Sections/DebugSettings/MemorySettings.cs b/osu.Game/Overlays/Settings/Sections/DebugSettings/MemorySettings.cs
index 84a54b208c..8d4fc5fc9f 100644
--- a/osu.Game/Overlays/Settings/Sections/DebugSettings/MemorySettings.cs
+++ b/osu.Game/Overlays/Settings/Sections/DebugSettings/MemorySettings.cs
@@ -33,10 +33,6 @@ namespace osu.Game.Overlays.Settings.Sections.DebugSettings
                         using (realmFactory.BlockAllOperations())
                         {
                         }
-
-                        // retrieve context to revive realm subscriptions.
-                        // TODO: should we do this from OsuGame or RealmContextFactory or something? Answer: yes.
-                        var _ = realmFactory.Context;
                     }
                 },
             };