--- old/src/hotspot/cpu/x86/templateInterpreterGenerator_x86.cpp	2018-09-26 10:02:27.145471453 -0400
+++ new/src/hotspot/cpu/x86/templateInterpreterGenerator_x86.cpp	2018-09-26 10:02:25.341366494 -0400
@@ -1090,19 +1090,17 @@
   __ movl(Address(thread, JavaThread::thread_state_offset()),
           _thread_in_native_trans);
 
-  if (os::is_MP()) {
-    if (UseMembar) {
-      // Force this write out before the read below
-      __ membar(Assembler::Membar_mask_bits(
-           Assembler::LoadLoad | Assembler::LoadStore |
-           Assembler::StoreLoad | Assembler::StoreStore));
-    } else {
-      // Write serialization page so VM thread can do a pseudo remote membar.
-      // We use the current thread pointer to calculate a thread specific
-      // offset to write to within the page. This minimizes bus traffic
-      // due to cache line collision.
-      __ serialize_memory(thread, rcx);
-    }
+  if (UseMembar) {
+    // Force this write out before the read below
+    __ membar(Assembler::Membar_mask_bits(
+                Assembler::LoadLoad | Assembler::LoadStore |
+                Assembler::StoreLoad | Assembler::StoreStore));
+  } else {
+    // Write serialization page so VM thread can do a pseudo remote membar.
+    // We use the current thread pointer to calculate a thread specific
+    // offset to write to within the page. This minimizes bus traffic
+    // due to cache line collision.
+    __ serialize_memory(thread, rcx);
   }
 
 #ifndef _LP64