The following test failed in the JDK18 CI:

vmTestbase/vm/gc/containers/LinkedHashMap_Arrays/TestDescription.java

Here's a snippet from the log file:

For random generator using seed: -7647663125500566696
To re-run test with same seed value please add "-Djdk.test.lib.random.seed=-7647663125500566696" to command line.
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=/g1DirtyCardQueue.cpp:173
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/opt/mach5/mesos/work_dir/slaves/ff806ead-2cac-495d-9cbc-62116f99bf14-S13868/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/334d6555-3d03-49dd-bfc6-052e608321d9/runs/209a2110-842a-4ce9-9ded-ac519d62191b/workspace/open/src/hotspot/share/gc/g1/g1DirtyCardQueue.cpp:173), pid=1769, tid=1778
# assert(actual == Atomic::load(&_num_cards)) failed: Num entries in completed buffers should be 30891 but are 11691
#
# JRE version: Java(TM) SE Runtime Environment (18.0+19) (fastdebug build 18-ea+19-1104)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 18-ea+19-1104, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0xc4c3c2] G1DirtyCardQueueSet::concatenate_logs()+0xf2
#
# Core dump will be written. Default location: Core dumps may be processed with "/opt/core.sh %p" (or dumping to /opt/mach5/mesos/work_dir/slaves/ff806ead-2cac-495d-9cbc-62116f99bf14-S13695/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/4ad20fff-55ed-448f-bf95-1c143397e368/runs/f3c0e739-2ca5-4f1e-8a7e-fb8454b4fc8f/testoutput/test-support/jtreg_open_test_hotspot_jtreg_vmTestbase_vm_gc_quick/scratch/1/core.1769)
#
# An error report file with more information is saved as:
# /opt/mach5/mesos/work_dir/slaves/ff806ead-2cac-495d-9cbc-62116f99bf14-S13695/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/4ad20fff-55ed-448f-bf95-1c143397e368/runs/f3c0e739-2ca5-4f1e-8a7e-fb8454b4fc8f/testoutput/test-support/jtreg_open_test_hotspot_jtreg_vmTestbase_vm_gc_quick/scratch/1/hs_err_pid1769.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(27/1278)----------

Here's the crashing thread's stack:

--------------- T H R E A D ---------------

Current thread (0x00007f28403deaf0): VMThread "VM Thread" [stack: 0x00007f28249d8000,0x00007f2824ad8000] [id=1778]

Stack: [0x00007f28249d8000,0x00007f2824ad8000], sp=0x00007f2824ad6060, free space=1016k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0xc4c3c2] G1DirtyCardQueueSet::concatenate_logs()+0xf2
V [libjvm.so+0xcf07fa] G1YoungCollector::pre_evacuate_collection_set(G1EvacInfo*, G1ParScanThreadStateSet*)+0x13a
V [libjvm.so+0xcf2791] G1YoungCollector::collect()+0x5d1
V [libjvm.so+0xc15777] G1CollectedHeap::do_collection_pause_at_safepoint_helper(double)+0xc7
V [libjvm.so+0xc158d3] G1CollectedHeap::do_collection_pause_at_safepoint(double)+0xa3
V [libjvm.so+0xcef4d8] VM_G1CollectForAllocation::doit()+0x68
V [libjvm.so+0x198eb9a] VM_Operation::evaluate()+0x18a
V [libjvm.so+0x19b21e3] VMThread::evaluate_operation(VM_Operation*)+0x183
V [libjvm.so+0x19b3057] VMThread::inner_execute(VM_Operation*)+0x3f7
V [libjvm.so+0x19b3185] VMThread::loop()+0xb5
V [libjvm.so+0x19b32ac] VMThread::run()+0xbc
V [libjvm.so+0x189a730] Thread::call_run()+0x100
V [libjvm.so+0x1577f24] thread_native_entry(Thread*)+0x104