Fix stack size variance between iterations (#3064)

* Fix stack size variance between iterations.

* Check cancellation after yield.

* Fix test

Author: timcassell

src/BenchmarkDotNet/Engines/Engine.cs

@@ -1,4 +1,4 @@
-using BenchmarkDotNet.Attributes.CompilerServices;
+using BenchmarkDotNet.Attributes.CompilerServices;
 using BenchmarkDotNet.Characteristics;
 using BenchmarkDotNet.Helpers;
 using BenchmarkDotNet.Jobs;
@@ -89,16 +89,19 @@ public async ValueTask<RunResults> RunAsync()
         }
 
         // This method is extra long because the helper methods were inlined in order to prevent extra async allocations on each iteration.
-        private async ValueTask<RunResults> RunCore()
+        private async Task<RunResults> RunCore()
         {
+            // We need to force an async yield here to ensure each benchmark invocation is called with a constant stack size. #1120
+            await Task.Yield();
+            Host.CancellationToken.ThrowIfCancellationRequested();
+
             var measurements = new List<Measurement>();
 
             if (EngineEventSource.Log.IsEnabled())
                 EngineEventSource.Log.BenchmarkStart(Parameters.BenchmarkName);
 
             IterationData extraIterationData = default;
-            // Enumerate the stages and run iterations in a loop to ensure each benchmark invocation is called with a constant stack size.
-            // #1120
+            // Enumerate the stages and run iterations in a loop to ensure each benchmark invocation is called with a constant stack size. #1120
             foreach (var stage in EngineStage.EnumerateStages(Parameters))
             {
                 if (stage.Stage == IterationStage.Actual && stage.Mode == IterationMode.Workload)

src/BenchmarkDotNet/Toolchains/InProcess/NoEmit/InProcessNoEmitRunner.cs

@@ -36,7 +36,7 @@ public static async ValueTask<int> Run(IHost host, ExecuteParameters parameters,
 
                 var methodInfo = type.GetMethod(nameof(Runnable.RunCore), BindingFlags.Public | BindingFlags.Static)
                     ?? throw new InvalidOperationException($"Bug: method {nameof(Runnable.RunCore)} in {inProcessRunnableTypeName} not found.");
-                await ((ValueTask) methodInfo.Invoke(null, [host, parameters, benchmarkActionFactory])!).ConfigureAwait(false);
+                await ((ValueTask) methodInfo.Invoke(null, [host, parameters, benchmarkActionFactory])!).ConfigureAwait(true);
 
                 return 0;
             }