--- a/src/hotspot/os/posix/os_posix.cpp	Mon Nov 25 12:32:40 2019 +0100
+++ b/src/hotspot/os/posix/os_posix.cpp	Mon Nov 25 12:33:15 2019 +0100
@@ -1900,7 +1900,7 @@
   // atomically decrement _event
   for (;;) {
     v = _event;
-    if (Atomic::cmpxchg(v - 1, &_event, v) == v) break;
+    if (Atomic::cmpxchg(&_event, v, v - 1) == v) break;
   }
   guarantee(v >= 0, "invariant");
 
@@ -1940,7 +1940,7 @@
   // atomically decrement _event
   for (;;) {
     v = _event;
-    if (Atomic::cmpxchg(v - 1, &_event, v) == v) break;
+    if (Atomic::cmpxchg(&_event, v, v - 1) == v) break;
   }
   guarantee(v >= 0, "invariant");