Fixed rare race condition in name table when deserializing on device with ARM processors (#2602)

Src/Newtonsoft.Json/DefaultJsonNameTable.cs

@@ -24,6 +24,7 @@
 #endregion
 
 using System;
+using System.Threading;
 
 namespace Newtonsoft.Json
 {
@@ -78,7 +79,12 @@ namespace Newtonsoft.Json
             hashCode -= hashCode >> 5;
 
             // make sure index is evaluated before accessing _entries, otherwise potential race condition causing IndexOutOfRangeException
-            var index = hashCode & _mask;
+#if NET20 || NET35 || NET40
+            int mask = Thread.VolatileRead(ref _mask);
+#else
+            int mask = Volatile.Read(ref _mask);
+#endif
+            var index = hashCode & mask;
             var entries = _entries;
 
             for (Entry entry = entries[index]; entry != null; entry = entry.Next)
@@ -160,7 +166,12 @@ namespace Newtonsoft.Json
                 }
             }
             _entries = newEntries;
-            _mask = newMask;
+
+#if NET20 || NET35 || NET40
+            Thread.VolatileWrite(ref _mask, newMask);
+#else
+            Volatile.Write(ref _mask, newMask);
+#endif
         }
 
         private static bool TextEquals(string str1, char[] str2, int str2Start, int str2Length)