diff --git a/build/Targets/Packages.props b/build/Targets/Packages.props
index ded34fefaae164b1f8d68155fb1837c9f4155503..555699313e810b8589cd16a39df4d2a8a9fea8cd 100644
--- a/build/Targets/Packages.props
+++ b/build/Targets/Packages.props
@@ -139,7 +139,7 @@
     <RestSharpVersion>105.2.3</RestSharpVersion>
     <RoslynBuildUtilVersion>0.9.8-beta</RoslynBuildUtilVersion>
     <RoslynDependenciesMicrosoftVisualStudioWorkspaceVersion>14.0.983-pre-ge167e81694</RoslynDependenciesMicrosoftVisualStudioWorkspaceVersion>
-    <RoslynDependenciesOptimizationDataVersion>2.3.0-beta3-61801-06</RoslynDependenciesOptimizationDataVersion>
+    <RoslynDependenciesOptimizationDataVersion>2.6.0-beta1-62010-04</RoslynDependenciesOptimizationDataVersion>
     <RoslynToolsMicrosoftLocateVSVersion>0.2.4-beta</RoslynToolsMicrosoftLocateVSVersion>
     <RoslynToolsMicrosoftSignToolVersion>0.3.0-beta</RoslynToolsMicrosoftSignToolVersion>
     <RoslynToolsMicrosoftVSIXExpInstallerVersion>0.4.0-beta</RoslynToolsMicrosoftVSIXExpInstallerVersion>
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenDeconstructTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenDeconstructTests.cs
index 7b7eb6dd69aa477dd5a65be946949edf6648e7a1..f08b0a714a17efbe00abd39d6e1aea6b88623de6 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenDeconstructTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenDeconstructTests.cs
@@ -7703,6 +7703,34 @@ static void Main()
             CompileAndVerify(comp, expectedOutput: "once");
         }
 
+        [WorkItem(21028, "https://github.com/dotnet/roslyn/issues/21028")]
+        [Fact]
+        public void InferredName()
+        {
+            var source =
+@"class C
+{
+    static void Main()
+    {
+        int x = 0, y = 1;
+        var t = (x, y);
+        var (a, b) = t;
+    }
+}";
+            // C# 7.0
+            var comp = CreateStandardCompilation(
+                source,
+                parseOptions: TestOptions.Regular.WithLanguageVersion(LanguageVersion.CSharp7),
+                references: new[] { ValueTupleRef, SystemRuntimeFacadeRef });
+            comp.VerifyEmitDiagnostics();
+            // C# 7.1
+            comp = CreateStandardCompilation(
+                source,
+                parseOptions: TestOptions.Regular.WithLanguageVersion(LanguageVersion.CSharp7_1),
+                references: new[] { ValueTupleRef, SystemRuntimeFacadeRef });
+            comp.VerifyEmitDiagnostics();
+        }
+
         [WorkItem(21028, "https://github.com/dotnet/roslyn/issues/21028")]
         [Fact]
         public void InferredName_ConditionalOperator()
diff --git a/src/VisualStudio/Core/Def/Implementation/TaskList/ExternalErrorDiagnosticUpdateSource.cs b/src/VisualStudio/Core/Def/Implementation/TaskList/ExternalErrorDiagnosticUpdateSource.cs
index e5646a59c81be9b5152c4884d7b1a633848d0900..e4091aa6fbbe84e5b0cccac66d878e056e1f4244 100644
--- a/src/VisualStudio/Core/Def/Implementation/TaskList/ExternalErrorDiagnosticUpdateSource.cs
+++ b/src/VisualStudio/Core/Def/Implementation/TaskList/ExternalErrorDiagnosticUpdateSource.cs
@@ -418,26 +418,29 @@ public void Done()
 
             public bool SupportedDiagnosticId(ProjectId projectId, string id)
             {
-                if (_diagnosticIdMap.TryGetValue(projectId, out var ids))
+                lock (_diagnosticIdMap)
                 {
-                    return ids.Contains(id);
-                }
+                    if (_diagnosticIdMap.TryGetValue(projectId, out var ids))
+                    {
+                        return ids.Contains(id);
+                    }
 
-                // set ids set
-                var map = new HashSet<string>();
-                _diagnosticIdMap.Add(projectId, map);
+                    // set ids set
+                    var map = new HashSet<string>();
+                    _diagnosticIdMap.Add(projectId, map);
 
-                var project = _solution.GetProject(projectId);
-                if (project == null)
-                {
-                    // projectId no longer exist, return false;
-                    return false;
-                }
+                    var project = _solution.GetProject(projectId);
+                    if (project == null)
+                    {
+                        // projectId no longer exist, return false;
+                        return false;
+                    }
 
-                var descriptorMap = _owner._diagnosticService.GetDiagnosticDescriptors(project);
-                map.UnionWith(descriptorMap.Values.SelectMany(v => v.Select(d => d.Id)));
+                    var descriptorMap = _owner._diagnosticService.GetDiagnosticDescriptors(project);
+                    map.UnionWith(descriptorMap.Values.SelectMany(v => v.Select(d => d.Id)));
 
-                return map.Contains(id);
+                    return map.Contains(id);
+                }
             }
 
             public ImmutableArray<DiagnosticData> GetBuildDiagnostics()
diff --git a/src/VisualStudio/Core/Test/Diagnostics/ExternalDiagnosticUpdateSourceTests.vb b/src/VisualStudio/Core/Test/Diagnostics/ExternalDiagnosticUpdateSourceTests.vb
index 9a62376bd18b8a488b5b623dafe293eeee54e2da..a05bd29372ac1860de28f583a56e7544d0155fec 100644
--- a/src/VisualStudio/Core/Test/Diagnostics/ExternalDiagnosticUpdateSourceTests.vb
+++ b/src/VisualStudio/Core/Test/Diagnostics/ExternalDiagnosticUpdateSourceTests.vb
@@ -68,6 +68,20 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.Diagnostics
             End Using
         End Sub
 
+        <Fact>
+        Public Sub TestExternalDiagnostics_SupportedDiagnosticId_Concurrent()
+            Using workspace = TestWorkspace.CreateCSharp(String.Empty)
+                Dim waiter = New Waiter()
+                Dim service = New TestDiagnosticAnalyzerService()
+                Dim source = New ExternalErrorDiagnosticUpdateSource(workspace, service, New MockDiagnosticUpdateSourceRegistrationService(), waiter)
+
+                Dim project = workspace.CurrentSolution.Projects.First()
+                source.OnSolutionBuild(Me, Shell.UIContextChangedEventArgs.From(True))
+
+                Parallel.For(0, 100, Sub(i As Integer) source.SupportedDiagnosticId(project.Id, "CS1002"))
+            End Using
+        End Sub
+
         <Fact>
         Public Async Function TestExternalDiagnostics_DuplicatedError() As Task
             Using workspace = TestWorkspace.CreateCSharp(String.Empty)