These errors have been seen in many RunThese24H runs, but in the past we then saw the access violation in get_thread_status() that was fixed by JDK-8269934, and the NPE was ignored:

[stress.process.err] java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because the return value of "java.lang.management.ThreadInfo.getLockName()" is null
[stress.process.err] at javasoft.sqe.tests.api.java.util.concurrent.JSR166TestCase.dumpTestThreads(JSR166TestCase.java:659)
[stress.process.err] at javasoft.sqe.tests.api.java.util.concurrent.JSR166TestCase.tearDownFail(JSR166TestCase.java:331)
[stress.process.err] at javasoft.sqe.tests.api.java.util.concurrent.JSR166TestCase.checkForkJoinPoolThreadLeaks(JSR166TestCase.java:387)
[stress.process.err] at javasoft.sqe.tests.api.java.util.concurrent.JSR166TestCase.tearDown(JSR166TestCase.java:364)
[stress.process.err] at javasoft.sqe.tests.api.junit.TestCase.invokeTestCase(TestCase.java:53)
[stress.process.err] at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:193)
[stress.process.err] at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:125)
[stress.process.err] at javasoft.sqe.tests.api.java.util.concurrent.LinkedBlockingDequeTest.main(LinkedBlockingDequeTest.java:51)
[stress.process.err] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[stress.process.err] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
[stress.process.err] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[stress.process.err] at java.base/java.lang.reflect.Method.invoke(Method.java:568)
[stress.process.err] at applications.kitchensink.process.stress.modules.JckStressModule$TestRunner$1.run(JckStressModule.java:275)

There are many such NPE's seen in the overall test times out. We also see many:

[stress.process.err] javasoft.sqe.tests.api.java.util.concurrent.CompletableFutureTest@410cadb8: ForkJoin common pool thread stuck