Fix failing debug assertion in JsonTypeInfo initialization (#67334)

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonTypeInfo.Cache.cs

@@ -6,6 +6,7 @@
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Threading;
 
 namespace System.Text.Json.Serialization.Metadata
 {
@@ -571,9 +572,16 @@ internal void UpdateSortedParameterCache(ref ReadStackFrame frame)
 
         internal void InitializePropCache()
         {
-            Debug.Assert(PropertyCache == null);
             Debug.Assert(PropertyInfoForTypeInfo.ConverterStrategy == ConverterStrategy.Object);
 
+            // Delayed JsonTypeInfo initialization can be invoked by
+            // multiple threads, add a temporary check to avoid contention.
+            // TODO refactor so that metadata initialization is single threaded.
+            if (Volatile.Read(ref PropertyCache) is not null)
+            {
+                return;
+            }
+
             JsonSerializerContext? context = Options.JsonSerializerContext;
             Debug.Assert(context != null);
 
@@ -620,16 +628,23 @@ internal void InitializePropCache()
                 CacheMember(jsonPropertyInfo, propertyCache, ref ignoredMembers);
             }
 
-            // Avoid threading issues by populating a local cache and assigning it to the global cache after completion.
-            PropertyCache = propertyCache;
+            // Populate a local cache and assign it to the global cache after completion.
+            Volatile.Write(ref PropertyCache, propertyCache);
         }
 
         internal void InitializeParameterCache()
         {
-            Debug.Assert(ParameterCache == null);
             Debug.Assert(PropertyCache != null);
             Debug.Assert(PropertyInfoForTypeInfo.ConverterStrategy == ConverterStrategy.Object);
 
+            // Delayed JsonTypeInfo initialization can be invoked by
+            // multiple threads, add a temporary check to avoid contention.
+            // TODO refactor so that metadata initialization is single threaded.
+            if (Volatile.Read(ref ParameterCache) is not null)
+            {
+                return;
+            }
+
             JsonSerializerContext? context = Options.JsonSerializerContext;
             Debug.Assert(context != null);
 

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonTypeInfo.cs

@@ -7,6 +7,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using System.Text.Json.Reflection;
+using System.Threading;
 
 namespace System.Text.Json.Serialization.Metadata
 {
@@ -487,8 +488,8 @@ private void InitializeConstructorParameters(JsonParameterInfoValues[] jsonParam
                 }
             }
 
-            ParameterCache = parameterCache;
             ParameterCount = jsonParameters.Length;
+            Volatile.Write(ref ParameterCache, parameterCache);
         }
 
         private static JsonParameterInfoValues[] GetParameterInfoArray(ParameterInfo[] parameters)