Add UniTaskSynchronizationContext, PlayerLoopHelper.IsInjectedUniTaskPlayerLoop, DumpCurrentPlayerLoop

README.md

@@ -384,6 +384,16 @@ var playerLoop = ScriptBehaviourUpdateOrder.CurrentPlayerLoop;
 PlayerLoopHelper.Initialize(ref playerLoop);
 ```
 
+You can diagnostic UniTask's player loop is ready by `PlayerLoopHelper.IsInjectedUniTaskPlayerLoop()`. And also `PlayerLoopHelper.DumpCurrentPlayerLoop` shows current all playerloop to console.
+
+```csharp
+void Start()
+{
+    UnityEngine.Debug.Log("UniTaskPlayerLoop ready? " + PlayerLoopHelper.IsInjectedUniTaskPlayerLoop());
+    PlayerLoopHelper.DumpCurrentPlayerLoop();
+}
+```
+
 async void vs async UniTaskVoid
 ---
 `async void` is a standard C# task system so does not run on UniTask systems. It is better not to use. `async UniTaskVoid` is a lightweight version of `async UniTask` because it does not have awaitable completion and report error immediately to `UniTaskScheduler.UnobservedTaskException`. If you don't require to await it(fire and forget), use `UniTaskVoid` is better. Unfortunately to dismiss warning, require to using with `Forget()`.
@@ -826,6 +836,23 @@ foreach (var (type, size) in TaskPool.GetCacheSizeInfo())
 
 > In UnityEditor profiler shows allocation of compiler generated AsyncStateMachine but it only occurs in debug(development) build. C# Compiler generate AsyncStateMachine as class on Debug build and as struct on Release build.
 
+UniTaskSynchronizationContext
+---
+Unity's default SynchronizationContext(`UnitySynchronizationContext`) is poor implementation for performance. UniTask itself is bypass `SynchronizationContext`(and `ExecutionContext`) so does not use it but if exists in `async Task`, still used it. `UniTaskSynchronizationContext` is replacement of `UnitySynchronizationContext`, it is better for performance.
+
+```csharp
+public class SyncContextInjecter
+{
+    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
+    public static void Inject()
+    {
+        SynchronizationContext.SetSynchronizationContext(new UniTaskSynchronizationContext());
+    }
+}
+```
+
+This is an optional choice and is not always recommended; `UniTaskSynchronizationContext` is less performance than `async UniTask` and is not a complete UniTask replacement. It also does not guarantee full behavioral compatibility with the `UnitySynchronizationContext`.
+
 API References
 ---
 UniTask's API References is hosted at [cysharp.github.io/UniTask](https://cysharp.github.io/UniTask/api/Cysharp.Threading.Tasks.html) by [DocFX](https://dotnet.github.io/docfx/) and [Cysharp/DocfXTemplate](https://github.com/Cysharp/DocfxTemplate).

src/UniTask/Assets/Plugins/UniTask/Runtime/PlayerLoopHelper.cs

@@ -175,6 +175,32 @@ namespace Cysharp.Threading.Tasks
             return dest;
         }
 
+        static PlayerLoopSystem[] InsertUniTaskSynchronizationContext(PlayerLoopSystem loopSystem)
+        {
+            var loop = new PlayerLoopSystem
+            {
+                type = typeof(UniTaskSynchronizationContext),
+                updateDelegate = UniTaskSynchronizationContext.Run
+            };
+
+            // Remove items from previous initializations.
+            var source = loopSystem.subSystemList
+                .Where(ls => ls.type != typeof(UniTaskSynchronizationContext))
+                .ToArray();
+
+            var dest = new System.Collections.Generic.List<PlayerLoopSystem>(source);
+
+            var index = dest.FindIndex(x => x.type.Name == "ScriptRunDelayedTasks");
+            if (index == -1)
+            {
+                index = dest.FindIndex(x => x.type.Name == "UniTaskLoopRunnerUpdate");
+            }
+
+            dest.Insert(index + 1, loop);
+
+            return dest.ToArray();
+        }
+
         [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
         static void Init()
         {
@@ -246,6 +272,8 @@ namespace Cysharp.Threading.Tasks
                     if (item != null) item.Run();
                 }
             }
+
+            UniTaskSynchronizationContext.Run();
         }
 
 #endif
@@ -293,6 +321,9 @@ namespace Cysharp.Threading.Tasks
                                                                   typeof(UniTaskLoopRunners.UniTaskLoopRunnerPostLateUpdate), runners[12] = new PlayerLoopRunner(PlayerLoopTiming.PostLateUpdate),
                                                                   typeof(UniTaskLoopRunners.UniTaskLoopRunnerLastPostLateUpdate), runners[13] = new PlayerLoopRunner(PlayerLoopTiming.LastPostLateUpdate));
 
+            // Insert UniTaskSynchronizationContext to Update loop
+            copyList[4].subSystemList = InsertUniTaskSynchronizationContext(copyList[4]);
+
             playerLoop.subSystemList = copyList;
             PlayerLoop.SetPlayerLoop(playerLoop);
         }
@@ -306,6 +337,56 @@ namespace Cysharp.Threading.Tasks
         {
             yielders[(int)timing].Enqueue(continuation);
         }
+
+        // Diagnostics helper
+
+#if UNITY_2019_3_OR_NEWER
+
+        public static void DumpCurrentPlayerLoop()
+        {
+            var playerLoop = UnityEngine.LowLevel.PlayerLoop.GetCurrentPlayerLoop();
+
+            var sb = new System.Text.StringBuilder();
+            sb.AppendLine($"PlayerLoop List");
+            foreach (var header in playerLoop.subSystemList)
+            {
+                sb.AppendFormat("------{0}------", header.type.Name);
+                sb.AppendLine();
+                foreach (var subSystem in header.subSystemList)
+                {
+                    sb.AppendFormat("{0}", subSystem.type.Name);
+                    sb.AppendLine();
+
+                    if (subSystem.subSystemList != null)
+                    {
+                        UnityEngine.Debug.LogWarning("More Subsystem:" + subSystem.subSystemList.Length);
+                    }
+                }
+            }
+
+            UnityEngine.Debug.Log(sb.ToString());
+        }
+
+        public static bool IsInjectedUniTaskPlayerLoop()
+        {
+            var playerLoop = UnityEngine.LowLevel.PlayerLoop.GetCurrentPlayerLoop();
+
+            foreach (var header in playerLoop.subSystemList)
+            {
+                foreach (var subSystem in header.subSystemList)
+                {
+                    if (subSystem.type == typeof(UniTaskLoopRunners.UniTaskLoopRunnerInitialization))
+                    {
+                        return true;
+                    }
+                }
+            }
+
+            return false;
+        }
+
+#endif
+
     }
 }
 

src/UniTask/Assets/Plugins/UniTask/Runtime/UniTaskSynchronizationContext.cs

@@ -0,0 +1,158 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace Cysharp.Threading.Tasks
+{
+    public class UniTaskSynchronizationContext : SynchronizationContext
+    {
+        const int MaxArrayLength = 0X7FEFFFFF;
+        const int InitialSize = 16;
+
+        static SpinLock gate = new SpinLock();
+        static bool dequing = false;
+
+        static int actionListCount = 0;
+        static Callback[] actionList = new Callback[InitialSize];
+
+        static int waitingListCount = 0;
+        static Callback[] waitingList = new Callback[InitialSize];
+
+        static int opCount;
+
+        public override void Send(SendOrPostCallback d, object state)
+        {
+            d(state);
+        }
+
+        public override void Post(SendOrPostCallback d, object state)
+        {
+            bool lockTaken = false;
+            try
+            {
+                gate.Enter(ref lockTaken);
+
+                if (dequing)
+                {
+                    // Ensure Capacity
+                    if (waitingList.Length == waitingListCount)
+                    {
+                        var newLength = waitingListCount * 2;
+                        if ((uint)newLength > MaxArrayLength) newLength = MaxArrayLength;
+
+                        var newArray = new Callback[newLength];
+                        Array.Copy(waitingList, newArray, waitingListCount);
+                        waitingList = newArray;
+                    }
+                    waitingList[waitingListCount] = new Callback(d, state);
+                    waitingListCount++;
+                }
+                else
+                {
+                    // Ensure Capacity
+                    if (actionList.Length == actionListCount)
+                    {
+                        var newLength = actionListCount * 2;
+                        if ((uint)newLength > MaxArrayLength) newLength = MaxArrayLength;
+
+                        var newArray = new Callback[newLength];
+                        Array.Copy(actionList, newArray, actionListCount);
+                        actionList = newArray;
+                    }
+                    actionList[actionListCount] = new Callback(d, state);
+                    actionListCount++;
+                }
+            }
+            finally
+            {
+                if (lockTaken) gate.Exit(false);
+            }
+        }
+
+        public override void OperationStarted()
+        {
+            Interlocked.Increment(ref opCount);
+        }
+
+        public override void OperationCompleted()
+        {
+            Interlocked.Decrement(ref opCount);
+        }
+
+        public override SynchronizationContext CreateCopy()
+        {
+            return this;
+        }
+
+        // delegate entrypoint.
+        internal static void Run()
+        {
+            {
+                bool lockTaken = false;
+                try
+                {
+                    gate.Enter(ref lockTaken);
+                    if (actionListCount == 0) return;
+                    dequing = true;
+                }
+                finally
+                {
+                    if (lockTaken) gate.Exit(false);
+                }
+            }
+
+            for (int i = 0; i < actionListCount; i++)
+            {
+                var action = actionList[i];
+                actionList[i] = default;
+                action.Invoke();
+            }
+
+            {
+                bool lockTaken = false;
+                try
+                {
+                    gate.Enter(ref lockTaken);
+                    dequing = false;
+
+                    var swapTempActionList = actionList;
+
+                    actionListCount = waitingListCount;
+                    actionList = waitingList;
+
+                    waitingListCount = 0;
+                    waitingList = swapTempActionList;
+                }
+                finally
+                {
+                    if (lockTaken) gate.Exit(false);
+                }
+            }
+        }
+
+        [StructLayout(LayoutKind.Auto)]
+        readonly struct Callback
+        {
+            readonly SendOrPostCallback callback;
+            readonly object state;
+
+            public Callback(SendOrPostCallback callback, object state)
+            {
+                this.callback = callback;
+                this.state = state;
+            }
+
+            public void Invoke()
+            {
+                try
+                {
+                    callback(state);
+                }
+                catch (Exception ex)
+                {
+                    UnityEngine.Debug.LogException(ex);
+                }
+            }
+        }
+    }
+}

src/UniTask/Assets/Plugins/UniTask/Runtime/UniTaskSynchronizationContext.cs.meta

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