In my tier1 runs on a heavily parallel machine, jdk/jshell/CustomInputToolBuilder.java fails intermittently. It only happens when it runs in the course of larger langtools:tier1, and the error suggests there is some other test that locks the default preferences storage.

$ CONF=linux-x86_64-server-fastdebug make run-test TEST=langtools:tier1

STDOUT:
config KullaTesting.setUp(): success
test CustomInputToolBuilder.checkCustomInput(): success
config KullaTesting.tearDown(): success
config KullaTesting.setUp(): success
test CustomInputToolBuilder.checkInteractiveTerminal(): failure
java.lang.IllegalStateException: java.util.prefs.BackingStoreException: Couldn't get file lock.
at jdk.jshell/jdk.internal.jshell.tool.JShellToolBuilder$PreferencesStorage.flush(JShellToolBuilder.java:313)
at jdk.jshell/jdk.internal.jshell.tool.ConsoleIOContext.close(ConsoleIOContext.java:291)
at jdk.jshell/jdk.internal.jshell.tool.JShellTool.start(JShellTool.java:997)
at jdk.jshell/jdk.internal.jshell.tool.JShellToolBuilder.start(JShellToolBuilder.java:261)
at CustomInputToolBuilder.doTest(CustomInputToolBuilder.java:91)
at CustomInputToolBuilder.checkInteractiveTerminal(CustomInputToolBuilder.java:109)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:132)
at org.testng.internal.TestInvoker.invokeMethod(TestInvoker.java:599)
at org.testng.internal.TestInvoker.invokeTestMethod(TestInvoker.java:174)
at org.testng.internal.MethodRunner.runInSequence(MethodRunner.java:46)
at org.testng.internal.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:822)
at org.testng.internal.TestInvoker.invokeTestMethods(TestInvoker.java:147)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:146)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:128)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.testng.TestRunner.privateRun(TestRunner.java:764)
at org.testng.TestRunner.run(TestRunner.java:585)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:384)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:378)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:337)
at org.testng.SuiteRunner.run(SuiteRunner.java:286)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:53)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:96)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1218)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1140)
at org.testng.TestNG.runSuites(TestNG.java:1069)
at org.testng.TestNG.run(TestNG.java:1037)
at com.sun.javatest.regtest.agent.TestNGRunner.main(TestNGRunner.java:94)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:312)
at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.util.prefs.BackingStoreException: Couldn't get file lock.
at java.prefs/java.util.prefs.FileSystemPreferences.sync(FileSystemPreferences.java:768)
at java.prefs/java.util.prefs.FileSystemPreferences.flush(FileSystemPreferences.java:863)
at jdk.jshell/jdk.internal.jshell.tool.JShellToolBuilder$PreferencesStorage.flush(JShellToolBuilder.java:311)
... 33 more

I believe this test should just run without default persistence to avoid this bug.