From 8557530cd5e744110b13a167ad30306c7224823e Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Fri, 1 Oct 2021 03:45:00 +0900
Subject: [PATCH 1/2] Add back main context locking

---
 osu.Game/Database/RealmContextFactory.cs | 30 ++++++++++++++++--------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/osu.Game/Database/RealmContextFactory.cs b/osu.Game/Database/RealmContextFactory.cs
index c51ac095bb..0e18b68276 100644
--- a/osu.Game/Database/RealmContextFactory.cs
+++ b/osu.Game/Database/RealmContextFactory.cs
@@ -37,6 +37,7 @@ namespace osu.Game.Database
         private static readonly GlobalStatistic<int> refreshes = GlobalStatistics.Get<int>("Realm", "Dirty Refreshes");
         private static readonly GlobalStatistic<int> contexts_created = GlobalStatistics.Get<int>("Realm", "Contexts (Created)");
 
+        private readonly object contextLock = new object();
         private Realm? context;
 
         public Realm Context
@@ -46,14 +47,17 @@ namespace osu.Game.Database
                 if (!ThreadSafety.IsUpdateThread)
                     throw new InvalidOperationException($"Use {nameof(CreateContext)} when performing realm operations from a non-update thread");
 
-                if (context == null)
+                lock (contextLock)
                 {
-                    context = createContext();
-                    Logger.Log($"Opened realm \"{context.Config.DatabasePath}\" at version {context.Config.SchemaVersion}");
-                }
+                    if (context == null)
+                    {
+                        context = createContext();
+                        Logger.Log($"Opened realm \"{context.Config.DatabasePath}\" at version {context.Config.SchemaVersion}");
+                    }
 
-                // creating a context will ensure our schema is up-to-date and migrated.
-                return context;
+                    // creating a context will ensure our schema is up-to-date and migrated.
+                    return context;
+                }
             }
         }
 
@@ -87,8 +91,11 @@ namespace osu.Game.Database
         {
             base.Update();
 
-            if (context?.Refresh() == true)
-                refreshes.Value++;
+            lock (contextLock)
+            {
+                if (context?.Refresh() == true)
+                    refreshes.Value++;
+            }
         }
 
         private Realm createContext()
@@ -137,8 +144,11 @@ namespace osu.Game.Database
 
             contextCreationLock.Wait();
 
-            context?.Dispose();
-            context = null;
+            lock (contextLock)
+            {
+                context?.Dispose();
+                context = null;
+            }
 
             return new InvokeOnDisposal<RealmContextFactory>(this, endBlockingSection);
 

From b51fd00ba34a8c201e79310834ca8e9ded9aeb4e Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Fri, 1 Oct 2021 03:46:53 +0900
Subject: [PATCH 2/2] Guard against disposal in all context retrievals

---
 osu.Game/Database/RealmContextFactory.cs | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/osu.Game/Database/RealmContextFactory.cs b/osu.Game/Database/RealmContextFactory.cs
index 0e18b68276..bf7feebdbf 100644
--- a/osu.Game/Database/RealmContextFactory.cs
+++ b/osu.Game/Database/RealmContextFactory.cs
@@ -51,7 +51,7 @@ namespace osu.Game.Database
                 {
                     if (context == null)
                     {
-                        context = createContext();
+                        context = CreateContext();
                         Logger.Log($"Opened realm \"{context.Config.DatabasePath}\" at version {context.Config.SchemaVersion}");
                     }
 
@@ -73,14 +73,6 @@ namespace osu.Game.Database
                 Filename += realm_extension;
         }
 
-        public Realm CreateContext()
-        {
-            if (IsDisposed)
-                throw new ObjectDisposedException(nameof(RealmContextFactory));
-
-            return createContext();
-        }
-
         /// <summary>
         /// Compact this realm.
         /// </summary>
@@ -98,8 +90,11 @@ namespace osu.Game.Database
             }
         }
 
-        private Realm createContext()
+        public Realm CreateContext()
         {
+            if (IsDisposed)
+                throw new ObjectDisposedException(nameof(RealmContextFactory));
+
             try
             {
                 contextCreationLock.Wait();
@@ -161,7 +156,10 @@ namespace osu.Game.Database
 
         protected override void Dispose(bool isDisposing)
         {
-            context?.Dispose();
+            lock (contextLock)
+            {
+                context?.Dispose();
+            }
 
             if (!IsDisposed)
             {