Improve .NET 9.0+ locking performance

Author: MarkCiliaVincenti

src/Discord.Net.Commands/Map/CommandMapNode.cs

@@ -2,6 +2,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Threading;
 
 namespace Discord.Commands
 {
@@ -11,7 +12,7 @@ internal class CommandMapNode
 
         private readonly ConcurrentDictionary<string, CommandMapNode> _nodes;
         private readonly string _name;
-        private readonly object _lockObj = new object();
+        private readonly Lock _lockObj = new();
         private ImmutableArray<CommandInfo> _commands;
 
         public bool IsEmpty => _commands.Length == 0 && _nodes.Count == 0;

src/Discord.Net.Core/Discord.Net.Core.csproj

@@ -19,5 +19,9 @@
     <PackageReference Include="IDisposableAnalyzers" Version="4.0.8">
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
+    <PackageReference Condition="!$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0'))" Include="Backport.System.Threading.Lock" Version="3.1.5">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>analyzers</IncludeAssets>
+    </PackageReference>  
   </ItemGroup>
 </Project>

src/Discord.Net.Rest/Entities/Interactions/CommandBase/RestCommandBase.cs

@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 
 using Model = Discord.API.Interaction;
@@ -32,7 +33,7 @@ public ulong CommandId
         /// </summary>
         internal new RestCommandBaseData Data { get; private set; }
 
-        private object _lock = new object();
+        private readonly Lock _lock = new();
 
         internal RestCommandBase(DiscordRestClient client, Model model)
             : base(client, model.Id)

src/Discord.Net.Rest/Entities/Interactions/MessageComponents/RestMessageComponent.cs

@@ -5,6 +5,7 @@
 using System.IO;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using DataModel = Discord.API.MessageComponentInteractionData;
 using Model = Discord.API.Interaction;
@@ -24,7 +25,7 @@ public class RestMessageComponent : RestInteraction, IComponentInteraction, IDis
         /// <inheritdoc cref="IComponentInteraction.Message"/>
         public RestUserMessage Message { get; private set; }
 
-        private object _lock = new object();
+        private readonly Lock _lock = new();
 
         internal RestMessageComponent(BaseDiscordClient client, Model model)
             : base(client, model.Id)

src/Discord.Net.Rest/Entities/Interactions/Modals/RestModal.cs

@@ -7,6 +7,7 @@
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Threading;
 using System.Threading.Tasks;
 
 using DataModel = Discord.API.ModalInteractionData;
@@ -41,7 +42,7 @@ internal RestModal(DiscordRestClient client, ModelBase model)
             return entity;
         }
 
-        private object _lock = new object();
+        private readonly Lock _lock = new();
 
         /// <summary>
         ///     Acknowledges this interaction with the <see cref="InteractionResponseType.DeferredUpdateMessage"/> if the modal was created

src/Discord.Net.Rest/Entities/Interactions/SlashCommands/RestAutocompleteInteraction.cs

@@ -3,6 +3,7 @@
 using System.IO;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using DataModel = Discord.API.AutocompleteInteractionData;
 using Model = Discord.API.Interaction;
@@ -19,7 +20,7 @@ public class RestAutocompleteInteraction : RestInteraction, IAutocompleteInterac
         /// </summary>
         public new RestAutocompleteInteractionData Data { get; }
 
-        private object _lock = new object();
+        private readonly Lock _lock = new();
 
         internal RestAutocompleteInteraction(DiscordRestClient client, Model model)
             : base(client, model.Id)

src/Discord.Net.Rest/Net/Queue/RequestQueueBucket.cs

@@ -17,7 +17,7 @@ internal class RequestBucket
     {
         private const int MinimumSleepTimeMs = 750;
 
-        private readonly object _lock;
+        private readonly Lock _lock;
         private readonly RequestQueue _queue;
         private int _semaphore;
         private DateTimeOffset? _resetTick;
@@ -32,7 +32,7 @@ public RequestBucket(RequestQueue queue, IRequest request, BucketId id)
             _queue = queue;
             Id = id;
 
-            _lock = new object();
+            _lock = new();
 
             if (request.Options.IsClientBucket)
                 WindowCount = ClientBucket.Get(request.Options.BucketId).WindowCount;

src/Discord.Net.WebSocket/DiscordShardedClient.cs

@@ -21,7 +21,7 @@ public partial class DiscordShardedClient : BaseSocketClient, IDiscordClient
         private ImmutableArray<StickerPack<SocketSticker>> _defaultStickers;
         private int _totalShards;
         private SemaphoreSlim[] _identifySemaphores;
-        private object _semaphoreResetLock;
+        private readonly Lock _semaphoreResetLock;
         private Task _semaphoreResetTask;
 
         private bool _isDisposed;
@@ -80,7 +80,7 @@ private DiscordShardedClient(int[] ids, DiscordSocketConfig config, API.DiscordS
             if (ids != null && config.TotalShards == null)
                 throw new ArgumentException($"Custom ids are not supported when {nameof(config.TotalShards)} is not specified.");
 
-            _semaphoreResetLock = new object();
+            _semaphoreResetLock = new();
             _shardIdsToIndex = new Dictionary<int, int>();
             config.DisplayInitialLog = false;
             _baseConfig = config;

src/Discord.Net.WebSocket/Entities/Channels/SocketThreadChannel.cs

@@ -6,6 +6,7 @@
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using Model = Discord.API.Channel;
 using ThreadMember = Discord.API.ThreadMember;
@@ -110,8 +111,8 @@ public bool IsPrivateThread
 
         private bool _usersDownloaded;
 
-        private readonly object _downloadLock = new object();
-        private readonly object _ownerLock = new object();
+        private readonly Lock _downloadLock = new();
+        private readonly Lock _ownerLock = new();
 
         private ulong _ownerId;
 

src/Discord.Net.WebSocket/Entities/Interaction/MessageComponents/SocketMessageComponent.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using DataModel = Discord.API.MessageComponentInteractionData;
 using Model = Discord.API.Interaction;
@@ -24,7 +25,7 @@ public class SocketMessageComponent : SocketInteraction, IComponentInteraction,
         /// <inheritdoc cref="IComponentInteraction.Message"/>
         public SocketUserMessage Message { get; private set; }
 
-        private object _lock = new object();
+        private readonly Lock _lock = new();
         public override bool HasResponded { get; internal set; } = false;
 
         internal SocketMessageComponent(DiscordSocketClient client, Model model, ISocketMessageChannel channel, SocketUser user)