Work around COM concurrency issue when accessing VS instances

Author: joeloff

src/Cli/dotnet/commands/dotnet-workload/list/VisualStudioWorkloads.cs

@@ -17,6 +17,8 @@ namespace Microsoft.DotNet.Workloads.Workload
 #endif
     internal static class VisualStudioWorkloads
     {
+        private static readonly object s_guard = new();
+
         private const int REGDB_E_CLASSNOTREG = unchecked((int)0x80040154);
 
         /// <summary>
@@ -125,44 +127,50 @@ internal static void GetInstalledWorkloads(IWorkloadResolver workloadResolver,
         /// <returns>A list of Visual Studio instances.</returns>
         private static List<ISetupInstance> GetVisualStudioInstances()
         {
-            List<ISetupInstance> vsInstances = new();
-
-            try
+            // The underlying COM API has a bug where-by it's not safe for concurrent calls. Until their
+            // bug fix is rolled out use a lock to ensure we don't concurrently access this API.
+            // https://dev.azure.com/devdiv/DevDiv/_workitems/edit/2241752/
+            lock (s_guard)
             {
-                SetupConfiguration setupConfiguration = new();
-                ISetupConfiguration2 setupConfiguration2 = setupConfiguration;
-                IEnumSetupInstances setupInstances = setupConfiguration2.EnumInstances();
-                ISetupInstance[] instances = new ISetupInstance[1];
-                int fetched = 0;
+                List<ISetupInstance> vsInstances = new();
 
-                do
+                try
                 {
-                    setupInstances.Next(1, instances, out fetched);
+                    SetupConfiguration setupConfiguration = new();
+                    ISetupConfiguration2 setupConfiguration2 = setupConfiguration;
+                    IEnumSetupInstances setupInstances = setupConfiguration2.EnumInstances();
+                    ISetupInstance[] instances = new ISetupInstance[1];
+                    int fetched = 0;
 
-                    if (fetched > 0)
+                    do
                     {
-                        ISetupInstance2 instance = (ISetupInstance2)instances[0];
+                        setupInstances.Next(1, instances, out fetched);
 
-                        // .NET Workloads only shipped in 17.0 and later and we should only look at IDE based SKUs
-                        // such as community, professional, and enterprise.
-                        if (Version.TryParse(instance.GetInstallationVersion(), out Version version) &&
-                            version.Major >= 17 &&
-                            s_visualStudioProducts.Contains(instance.GetProduct().GetId()))
+                        if (fetched > 0)
                         {
-                            vsInstances.Add(instances[0]);
+                            ISetupInstance2 instance = (ISetupInstance2)instances[0];
+
+                            // .NET Workloads only shipped in 17.0 and later and we should only look at IDE based SKUs
+                            // such as community, professional, and enterprise.
+                            if (Version.TryParse(instance.GetInstallationVersion(), out Version version) &&
+                                version.Major >= 17 &&
+                                s_visualStudioProducts.Contains(instance.GetProduct().GetId()))
+                            {
+                                vsInstances.Add(instances[0]);
+                            }
                         }
                     }
+                    while (fetched > 0);
+
+                }
+                catch (COMException e) when (e.ErrorCode == REGDB_E_CLASSNOTREG)
+                {
+                    // Query API not registered, good indication there are no VS installations of 15.0 or later.
+                    // Other exceptions are passed through since that likely points to a real error.
                 }
-                while (fetched > 0);
 
+                return vsInstances;
             }
-            catch (COMException e) when (e.ErrorCode == REGDB_E_CLASSNOTREG)
-            {
-                // Query API not registered, good indication there are no VS installations of 15.0 or later.
-                // Other exceptions are passed through since that likely points to a real error.
-            }
-
-            return vsInstances;
         }
     }
 }