Hi there! Seems that following [1] outcome should be forbidden in JMM. It violates synchronization order between unlock and lock actions on a monitor, doesn't it? [1] http://hg.openjdk.java.net/code-tools/jcstress/file/64f2cf32fa0a/jcstress-samples/src/main/java/org/openjdk/jcstress/samples/JMMSample_04_PartialOrder.java#l192 Sincerely, Vadim