From aa68ae4ff27713f25ad42545baa905d83e29de4f Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Tue, 8 Dec 2020 20:10:23 +0900
Subject: [PATCH] Change locking mechanism for multiplayer rooms to use
 using-disposal pattern

Was required to lock over `await` calls server-side.
---
 .../RealtimeMultiplayer/LockUntilDisposal.cs  | 24 +++++++++++++++++++
 .../RealtimeMultiplayer/MultiplayerRoom.cs    |  9 ++-----
 2 files changed, 26 insertions(+), 7 deletions(-)
 create mode 100644 osu.Game/Online/RealtimeMultiplayer/LockUntilDisposal.cs

diff --git a/osu.Game/Online/RealtimeMultiplayer/LockUntilDisposal.cs b/osu.Game/Online/RealtimeMultiplayer/LockUntilDisposal.cs
new file mode 100644
index 0000000000..cd16fce2ee
--- /dev/null
+++ b/osu.Game/Online/RealtimeMultiplayer/LockUntilDisposal.cs
@@ -0,0 +1,24 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Threading;
+
+namespace osu.Game.Online.RealtimeMultiplayer
+{
+    public readonly struct LockUntilDisposal : IDisposable
+    {
+        private readonly object lockTarget;
+
+        public LockUntilDisposal(object lockTarget)
+        {
+            this.lockTarget = lockTarget;
+            Monitor.Enter(lockTarget);
+        }
+
+        public void Dispose()
+        {
+            Monitor.Exit(lockTarget);
+        }
+    }
+}
diff --git a/osu.Game/Online/RealtimeMultiplayer/MultiplayerRoom.cs b/osu.Game/Online/RealtimeMultiplayer/MultiplayerRoom.cs
index 3fbc01a2f5..0f18ab6c89 100644
--- a/osu.Game/Online/RealtimeMultiplayer/MultiplayerRoom.cs
+++ b/osu.Game/Online/RealtimeMultiplayer/MultiplayerRoom.cs
@@ -5,7 +5,6 @@
 
 using System;
 using System.Collections.Generic;
-using JetBrains.Annotations;
 
 namespace osu.Game.Online.RealtimeMultiplayer
 {
@@ -48,12 +47,8 @@ namespace osu.Game.Online.RealtimeMultiplayer
         }
 
         /// <summary>
-        /// Perform an update on this room in a thread-safe manner.
+        /// Request a lock on this room to perform a thread-safe update.
         /// </summary>
-        /// <param name="action">The action to perform.</param>
-        public void PerformUpdate([InstantHandle] Action<MultiplayerRoom> action)
-        {
-            lock (writeLock) action(this);
-        }
+        public LockUntilDisposal LockForUpdate() => new LockUntilDisposal(writeLock);
     }
 }