The following test failed in the JDK20 CI:

gc/TestFullGCCount.java

Here's a snippet from linux-x64-debug log file:

#-----testdescription-----
$file=/opt/mach5/mesos/work_dir/jib-master/install/jdk-20+28-2237/src.full/open/test/hotspot/jtreg/gc/TestFullGCCount.java
$root=/opt/mach5/mesos/work_dir/jib-master/install/jdk-20+28-2237/src.full/open/test/hotspot/jtreg
keywords=bug7072527 othervm
modules=java.management
requires=((\!(vm.gc \=\= "Shenandoah" & vm.opt.ExplicitGCInvokesConcurrent \!\= false)) & (\!(vm.gc \=\= "G1" & vm.opt.ExplicitGCInvokesConcurrent))) & (vm.gc \!\= "Z")
run=USER_SPECIFIED main/othervm -Xlog\:gc gc.TestFullGCCount\n
source=TestFullGCCount.java
title=JMM GC counters overcount in some cases

#-----environment-----

#-----testresult-----
description=file\:/opt/mach5/mesos/work_dir/jib-master/install/jdk-20+28-2237/src.full/open/test/hotspot/jtreg/gc/TestFullGCCount.java
end=Wed Dec 14 16\:01\:53 UTC 2022
environment=regtest
execStatus=Error. Error evaluating expression\: invalid boolean value\: `null' for expression `vm.opt.ExplicitGCInvokesConcurrent'
harnessLoaderMode=Classpath Loader
harnessVariety=Full Bundle
javatestOS=Linux 5.4.17-2136.306.1.3.el7uek.x86_64 (amd64)
javatestVersion=6.0-ea+b24-2022-09-27-9149bb7
script=com.sun.javatest.regtest.exec.RegressionScript
sections=script_messages
start=Wed Dec 14 16\:01\:53 UTC 2022
test=gc/TestFullGCCount.java
totalTime=0
work=/opt/mach5/mesos/work_dir/slaves/0c72054a-24ab-4dbb-944f-97f9341a1b96-S94857/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/7b7789ac-d8be-4c51-b9a8-328e7e834a09/runs/c8740748-0f26-4b9a-8f79-9a1733869edb/testoutput/test-support/jtreg_open_test_hotspot_jtreg_hotspot_gc/gc

#section:script_messages
----------messages:(0/0)----------


test result: Error. Error evaluating expression: invalid boolean value: `null' for expression `vm.opt.ExplicitGCInvokesConcurrent'

I'm starting this as a P2 since it looks like a regression due to:

JDK-8298296 gc/TestFullGCCount.java fails with "System.gc collections miscounted."