Run this test (java/awt/security/WarningWindowDisposeTest/WarningWindowDisposeTest.java) on Ubuntu Unity with some build of JDK9 before b129 or after a PIT build for b141 (including). (Builds b130 -- b140 have a bug JDK-8162102).

The test fails consistently for me with java.lang.RuntimeException: Test FAILED! The child process never exits

It is a test bug, in my opinion. A waiting TimeoutThread sleeps for some time and then checks the status of an AtomicBoolean; if we make that sleep time twice as big, the value of that AtomicBoolean is always true and the test pass. Visually, a warning window disappears properly, too.