--- old/src/hotspot/share/utilities/singleWriterSynchronizer.cpp	2019-11-21 11:58:41.596524575 +0100
+++ new/src/hotspot/share/utilities/singleWriterSynchronizer.cpp	2019-11-21 11:58:41.164517281 +0100
@@ -44,7 +44,7 @@
 // synchronization have exited that critical section.
 void SingleWriterSynchronizer::synchronize() {
   // Side-effect in assert balanced by debug-only dec at end.
-  assert(Atomic::add(1u, &_writers) == 1u, "multiple writers");
+  assert(Atomic::add(&_writers, 1u) == 1u, "multiple writers");
   // We don't know anything about the muxing between this invocation
   // and invocations in other threads.  We must start with the latest
   // _enter polarity, else we could clobber the wrong _exit value on
@@ -64,7 +64,7 @@
   do {
     old = value;
     *new_ptr = ++value;
-    value = Atomic::cmpxchg(value, &_enter, old);
+    value = Atomic::cmpxchg(&_enter, old, value);
   } while (old != value);
   // Critical sections entered before we changed the polarity will use
   // the old exit counter.  Critical sections entered after the change