The following test timed out in the JDK15 CI:

java/lang/management/ThreadMXBean/ThreadMXBeanStateTest.java

Here's a snippet from the log file:

#section:main
----------messages:(8/233)----------
command: main ThreadMXBeanStateTest
reason: User specified action: run main ThreadMXBeanStateTest
Mode: agentvm
Agent id: 7
Timeout refired 480 times
Timeout information:
--- Timeout information end.
elapsed time (seconds): 500.829
----------configuration:(15/2152)----------
Boot Layer
  class path: /opt/mach5/mesos/work_dir/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/javatest.jar
              /opt/mach5/mesos/work_dir/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/jtreg.jar
              /opt/mach5/mesos/work_dir/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/junit.jar
              /opt/mach5/mesos/work_dir/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/testng.jar
  patch: java.base /opt/mach5/mesos/work_dir/slaves/4728e7c1-7e67-490e-be0f-6bbf2a2f33db-S202/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/ccc373ce-4672-449a-8940-b8c134b36d59/runs/2ab15276-9594-4d6a-8693-8df0281b9518/testoutput/test-support/jtreg_open_test_jdk_jdk_management/patches/java.base

Test Layer
  class path: /opt/mach5/mesos/work_dir/slaves/4728e7c1-7e67-490e-be0f-6bbf2a2f33db-S202/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/ccc373ce-4672-449a-8940-b8c134b36d59/runs/2ab15276-9594-4d6a-8693-8df0281b9518/testoutput/test-support/jtreg_open_test_jdk_jdk_management/classes/0/java/lang/management/ThreadMXBean/ThreadMXBeanStateTest.d
              /opt/mach5/mesos/work_dir/jib-master/install/jdk-15+27-1370/src.full/open/test/jdk/java/lang/management/ThreadMXBean
              /opt/mach5/mesos/work_dir/slaves/4728e7c1-7e67-490e-be0f-6bbf2a2f33db-S202/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/ccc373ce-4672-449a-8940-b8c134b36d59/runs/2ab15276-9594-4d6a-8693-8df0281b9518/testoutput/test-support/jtreg_open_test_jdk_jdk_management/classes/0/test/lib
              /opt/mach5/mesos/work_dir/jib-master/install/jdk-15+27-1370/src.full/open/test/lib
              /opt/mach5/mesos/work_dir/slaves/4728e7c1-7e67-490e-be0f-6bbf2a2f33db-S202/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/ccc373ce-4672-449a-8940-b8c134b36d59/runs/2ab15276-9594-4d6a-8693-8df0281b9518/testoutput/test-support/jtreg_open_test_jdk_jdk_management/classes/0/java/lang/Thread
              /opt/mach5/mesos/work_dir/jib-master/install/jdk-15+27-1370/src.full/open/test/jdk/java/lang/Thread

----------rerun:(31/6616)*----------

The fix for the following bug was pushed recently:

    JDK-8081652 [TESTBUG] java/lang/management/ThreadMXBean/ThreadMXBeanStateTest.java timed out intermittently

However, this sighting happened a couple of days after the push.