From 93cbc0974aa0475c586f40645e5b58a4b08ef017 Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Tue, 24 Nov 2020 20:25:27 -0500
Subject: [PATCH] Remove ForceAsync from CryptoStream (#45150)

---
 .../Threading/Tasks/ForceAsyncAwaiter.cs      | 45 -------------------
 .../src/System.IO.Pipes.csproj                |  2 -
 ...em.Security.Cryptography.Primitives.csproj |  2 -
 .../Security/Cryptography/CryptoStream.cs     | 12 ++---
 4 files changed, 6 insertions(+), 55 deletions(-)
 delete mode 100644 src/libraries/Common/src/System/Threading/Tasks/ForceAsyncAwaiter.cs

diff --git a/src/libraries/Common/src/System/Threading/Tasks/ForceAsyncAwaiter.cs b/src/libraries/Common/src/System/Threading/Tasks/ForceAsyncAwaiter.cs
deleted file mode 100644
index 9b5d88f5b993b..0000000000000
--- a/src/libraries/Common/src/System/Threading/Tasks/ForceAsyncAwaiter.cs
+++ /dev/null
@@ -1,45 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-using System.Runtime.CompilerServices;
-
-namespace System.Threading.Tasks
-{
-    internal static partial class TaskAwaiters
-    {
-        /// <summary>
-        /// Returns an awaitable/awaiter that will ensure the continuation is executed
-        /// asynchronously on the thread pool, even if the task is already completed
-        /// by the time the await occurs.  Effectively, it is equivalent to awaiting
-        /// with ConfigureAwait(false) and then queuing the continuation with Task.Run,
-        /// but it avoids the extra hop if the continuation already executed asynchronously.
-        /// </summary>
-        public static ForceAsyncAwaiter ForceAsync(this Task task)
-        {
-            return new ForceAsyncAwaiter(task);
-        }
-    }
-
-    internal readonly struct ForceAsyncAwaiter : ICriticalNotifyCompletion
-    {
-        private readonly Task _task;
-
-        internal ForceAsyncAwaiter(Task task) { _task = task; }
-
-        public ForceAsyncAwaiter GetAwaiter() { return this; }
-
-        public bool IsCompleted { get { return false; } } // the purpose of this type is to always force a continuation
-
-        public void GetResult() { _task.GetAwaiter().GetResult(); }
-
-        public void OnCompleted(Action action)
-        {
-            _task.ConfigureAwait(false).GetAwaiter().OnCompleted(action);
-        }
-
-        public void UnsafeOnCompleted(Action action)
-        {
-            _task.ConfigureAwait(false).GetAwaiter().UnsafeOnCompleted(action);
-        }
-    }
-}
diff --git a/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj b/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj
index 66f0da7b4d6a6..a89cd7202c08e 100644
--- a/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj
+++ b/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj
@@ -167,8 +167,6 @@
              Link="Common\Interop\Unix\Interop.GetEUid.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.SetEUid.cs"
              Link="Common\Interop\Unix\Interop.SetEUid.cs" />
-    <Compile Include="$(CommonPath)System\Threading\Tasks\ForceAsyncAwaiter.cs"
-             Link="Common\System\Threading\Tasks\ForceAsyncAwaiter.cs" />
   </ItemGroup>
   <ItemGroup>
     <Reference Include="System.Collections" />
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj b/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj
index 681bb084de8ac..e75bb29692d4f 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj
@@ -25,8 +25,6 @@
     <Compile Include="System\Security\Cryptography\SymmetricAlgorithm.cs" />
     <Compile Include="$(CommonPath)System\Obsoletions.cs"
              Link="Common\System\Obsoletions.cs" />
-    <Compile Include="$(CommonPath)System\Threading\Tasks\ForceAsyncAwaiter.cs"
-             Link="Common\System\Threading\Tasks\ForceAsyncAwaiter.cs" />
     <Compile Include="$(CommonPath)Internal\Cryptography\Helpers.cs"
              Link="Internal\Cryptography\Helpers.cs" />
     <Compile Include="$(CommonPath)System\Security\Cryptography\CryptoPool.cs"
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/CryptoStream.cs b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/CryptoStream.cs
index 74dca0fba912b..ff5003d7bc78a 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/CryptoStream.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/CryptoStream.cs
@@ -3,6 +3,7 @@
 
 using System.Buffers;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
@@ -218,15 +219,14 @@ private async Task<int> ReadAsyncInternal(byte[] buffer, int offset, int count,
             // async requests outstanding, we will block the application's main
             // thread if it does a second IO request until the first one completes.
 
-            SemaphoreSlim semaphore = AsyncActiveSemaphore;
-            await semaphore.WaitAsync(cancellationToken).ForceAsync();
+            await AsyncActiveSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
             try
             {
                 return await ReadAsyncCore(buffer, offset, count, cancellationToken, useAsync: true).ConfigureAwait(false);
             }
             finally
             {
-                semaphore.Release();
+                _lazyAsyncActiveSemaphore.Release();
             }
         }
 
@@ -495,15 +495,14 @@ private async Task WriteAsyncInternal(byte[] buffer, int offset, int count, Canc
             // async requests outstanding, we will block the application's main
             // thread if it does a second IO request until the first one completes.
 
-            SemaphoreSlim semaphore = AsyncActiveSemaphore;
-            await semaphore.WaitAsync(cancellationToken).ForceAsync();
+            await AsyncActiveSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
             try
             {
                 await WriteAsyncCore(buffer, offset, count, cancellationToken, useAsync: true).ConfigureAwait(false);
             }
             finally
             {
-                semaphore.Release();
+                _lazyAsyncActiveSemaphore.Release();
             }
         }
 
@@ -748,6 +747,7 @@ private void InitializeBuffer()
             }
         }
 
+        [MemberNotNull(nameof(_lazyAsyncActiveSemaphore))]
         private SemaphoreSlim AsyncActiveSemaphore
         {
             get