Expose members of ExecutionContext and AsyncFlowControl (dotnet/coreclr#8107)

Expose members of ExecutionContext and AsyncFlowControl

- Fix ExecutionContext.Capture and AsyncFlowControl.Undo when flow is suppressed
- Expose deserialization constructor for ExecutionContext

Commit migrated from https://github.com/dotnet/coreclr/commit/2246c1ff94cbd84df83e5308c81a1d1018c3f154

diff --git a/src/coreclr/src/mscorlib/model.xml b/src/coreclr/src/mscorlib/model.xml
index 1e041a8..c47940e 100644 (file)
--- a/src/coreclr/src/mscorlib/model.xml
+++ b/src/coreclr/src/mscorlib/model.xml
@@ -7994,6 +7994,15 @@
       <Member MemberType="Field" Name="Unknown" />
       <Member MemberType="Field" Name="value__" />
     </Type>
+    <Type Name="System.Threading.AsyncFlowControl">
+      <Member Name="Dispose" />
+      <Member Name="Equals(System.Object)" />
+      <Member Name="Equals(System.Threading.AsyncFlowControl)" />
+      <Member Name="GetHashCode" />
+      <Member Name="op_Equality(System.Threading.AsyncFlowControl,System.Threading.AsyncFlowControl)" />
+      <Member Name="op_Inequality(System.Threading.AsyncFlowControl,System.Threading.AsyncFlowControl)" />
+      <Member Name="Undo" />
+    </Type>
     <Type Name="System.Threading.AutoResetEvent">
       <Member Name="#ctor(System.Boolean)" />
     </Type>
@@ -12181,8 +12190,15 @@
       <Member Name="get_ThreadContextChanged"/>
     </Type>
     <Type Name="System.Threading.ExecutionContext">
+      <Member Status="ImplRoot" Name="#ctor(System.Runtime.Serialization.SerializationInfo,System.Runtime.Serialization.StreamingContext)" />
       <Member Name="Capture" />
+      <Member Name="CreateCopy" />
+      <Member Name="Dispose" />
+      <Member Name="GetObjectData(System.Runtime.Serialization.SerializationInfo,System.Runtime.Serialization.StreamingContext)" />
+      <Member Name="IsFlowSuppressed" />
+      <Member Name="RestoreFlow" />
       <Member Name="Run(System.Threading.ExecutionContext,System.Threading.ContextCallback,System.Object)"/>
+      <Member Name="SuppressFlow" />
     </Type>
     <Type Name="System.Threading.CancellationToken">
       <Member Name="#ctor(System.Boolean)"/>

diff --git a/src/coreclr/src/mscorlib/src/System.Private.CoreLib.txt b/src/coreclr/src/mscorlib/src/System.Private.CoreLib.txt
index d1eb712..7d3d240 100644 (file)
--- a/src/coreclr/src/mscorlib/src/System.Private.CoreLib.txt
+++ b/src/coreclr/src/mscorlib/src/System.Private.CoreLib.txt
@@ -1250,7 +1250,7 @@ InvalidOperation_CannotUseAFCOtherThread = AsyncFlowControl object must be used
 InvalidOperation_CannotRestoreUnsupressedFlow = Cannot restore context flow when it is not suppressed.
 InvalidOperation_CannotSupressFlowMultipleTimes = Context flow is already suppressed.
 InvalidOperation_CannotUseAFCMultiple = AsyncFlowControl object can be used only once to call Undo().
-InvalidOperation_AsyncFlowCtrlCtxMismatch = AsyncFlowControl objects can be used to restore flow only on the Context that had its flow suppressed.
+InvalidOperation_AsyncFlowCtrlCtxMismatch = AsyncFlowControl objects can be used to restore flow only on a Context that had its flow suppressed.
 InvalidOperation_TimeoutsNotSupported = Timeouts are not supported on this stream.
 InvalidOperation_Overlapped_Pack = Cannot pack a packed Overlapped again.
 InvalidOperation_OnlyValidForDS = Adding ACEs with Object Flags and Object GUIDs is only valid for directory-object ACLs.

diff --git a/src/coreclr/src/mscorlib/src/System/Threading/ExecutionContext.cs b/src/coreclr/src/mscorlib/src/System/Threading/ExecutionContext.cs
index f4926ef..f0b7067 100644 (file)
--- a/src/coreclr/src/mscorlib/src/System/Threading/ExecutionContext.cs
+++ b/src/coreclr/src/mscorlib/src/System/Threading/ExecutionContext.cs
@@ -105,7 +105,16 @@ namespace System.Threading
         public static ExecutionContext Capture()
         {
             ExecutionContext executionContext = Thread.CurrentThread.ExecutionContext;
-            return executionContext == null || executionContext.m_isFlowSuppressed ? Default : executionContext;
+            if (executionContext == null)
+            {
+                return Default;
+            }
+            if (executionContext.m_isFlowSuppressed)
+            {
+                // Prevent ExecutionContext.Run on a suppressed-flow context for desktop framework compatibility
+                return null;
+            }
+            return executionContext;
         }
 
         private ExecutionContext ShallowClone(bool isFlowSuppressed)
@@ -116,7 +125,7 @@ namespace System.Threading
                 m_localValues == Default.m_localValues &&
                 m_localChangeNotifications == Default.m_localChangeNotifications)
             {
-                return null; // implies default context
+                return null; // implies the default context
             }
             return new ExecutionContext(m_localValues, m_localChangeNotifications, isFlowSuppressed);
         }
@@ -134,7 +143,7 @@ namespace System.Threading
             executionContext = executionContext.ShallowClone(isFlowSuppressed: true);
             var asyncFlowControl = new AsyncFlowControl();
             currentThread.ExecutionContext = executionContext;
-            asyncFlowControl.Initialize(currentThread, executionContext);
+            asyncFlowControl.Initialize(currentThread);
             return asyncFlowControl;
         }
 
@@ -383,16 +392,11 @@ namespace System.Threading
     public struct AsyncFlowControl : IDisposable
     {
         private Thread _thread;
-        private ExecutionContext _executionContext;
 
-        internal void Initialize(Thread currentThread, ExecutionContext executionContext)
+        internal void Initialize(Thread currentThread)
         {
             Contract.Assert(currentThread == Thread.CurrentThread);
-            Contract.Assert(executionContext != null);
-            Contract.Assert(executionContext == currentThread.ExecutionContext);
-
             _thread = currentThread;
-            _executionContext = executionContext;
         }
 
         public void Undo()
@@ -405,7 +409,18 @@ namespace System.Threading
             {
                 throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_CannotUseAFCOtherThread"));
             }
-            if (_thread.ExecutionContext != _executionContext)
+
+            // An async flow control cannot be undone when a different execution context is applied. The desktop framework
+            // mutates the execution context when its state changes, and only changes the instance when an execution context
+            // is applied (for instance, through ExecutionContext.Run). The framework prevents a suppressed-flow execution
+            // context from being applied by returning null from ExecutionContext.Capture, so the only type of execution
+            // context that can be applied is one whose flow is not suppressed. After suppressing flow and changing an async
+            // local's value, the desktop framework verifies that a different execution context has not been applied by
+            // checking the execution context instance against the one saved from when flow was suppressed. In .NET Core,
+            // since the execution context instance will change after changing the async local's value, it verifies that a
+            // different execution context has not been applied, by instead ensuring that the current execution context's
+            // flow is suppressed.
+            if (!ExecutionContext.IsFlowSuppressed())
             {
                 throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_AsyncFlowCtrlCtxMismatch"));
             }
@@ -427,12 +442,12 @@ namespace System.Threading
 
         public bool Equals(AsyncFlowControl obj)
         {
-            return _thread == obj._thread && _executionContext == obj._executionContext;
+            return _thread == obj._thread;
         }
 
         public override int GetHashCode()
         {
-            return (_thread?.GetHashCode() ?? 0) + (_executionContext?.GetHashCode() ?? 0);
+            return _thread?.GetHashCode() ?? 0;
         }
 
         public static bool operator ==(AsyncFlowControl a, AsyncFlowControl b)