The following test failed in the JDK16 CI:

applications/kitchensink/Kitchensink.java

Here's a snippet from the log file:

Iteration start: LockDeflation at Sun Jun 28 22:30:37 UTC 2020
Iteration done: MemAccess at Sun Jun 28 22:31:02 UTC 2020
Iteration done: SpecJvm2008Batch at Sun Jun 28 22:31:07 UTC 2020
Iteration start: SpecJvm2008Batch at Sun Jun 28 22:31:07 UTC 2020
Iteration done: LockDeflation at Sun Jun 28 22:31:15 UTC 2020
Iteration start: MemAccess at Sun Jun 28 22:32:02 UTC 2020


The tail of stress stdout is:
For random generator using seed: -828827228002506869
To re-run test with same seed value please add "-Djdk.test.lib.random.seed=-828827228002506869" to command line.
Stress process main method is started.
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f27a667b3be, pid=6760, tid=6827
#
# JRE version: Java(TM) SE Runtime Environment (16.0+4) (build 16-ea+4-99)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (16-ea+4-99, mixed mode, sharing, tiered, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x69e3be] G1ScanHRForRegionClosure::scan_heap_roots(HeapRegion*)+0xa6e
#
# 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/4728e7c1-7e67-490e-be0f-6bbf2a2f33db-S57/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/eb174d08-460e-4623-82ee-217b486baca8/runs/1ca75b9f-c575-4bc1-a4e0-28d2da51dca0/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_kitchensink_Kitchensink_java/scratch/0/core.6760)
#
Unsupported internal testing APIs have been used.

# An error report file with more information is saved as:
# /opt/mach5/mesos/work_dir/slaves/4728e7c1-7e67-490e-be0f-6bbf2a2f33db-S57/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/eb174d08-460e-4623-82ee-217b486baca8/runs/1ca75b9f-c575-4bc1-a4e0-28d2da51dca0/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_kitchensink_Kitchensink_java/scratch/0/hs_err_pid6760.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(242/22586)----------


Here's the crashing thread's stack:

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

Current thread (0x00007f2360001f80): GCTaskThread "GC Thread#2" [stack: 0x00007f2365b59000,0x00007f2365c59000] [id=6827]

Stack: [0x00007f2365b59000,0x00007f2365c59000], sp=0x00007f2365c57b00, free space=1018k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x69e3be] G1ScanHRForRegionClosure::scan_heap_roots(HeapRegion*)+0xa6e
V [libjvm.so+0x695bc5] G1RemSet::scan_heap_roots(G1ParScanThreadState*, unsigned int, G1GCPhaseTimes::GCParPhases, G1GCPhaseTimes::GCParPhases)+0x1b5
V [libjvm.so+0x641a93] G1EvacuateRegionsTask::scan_roots(G1ParScanThreadState*, unsigned int)+0x43
V [libjvm.so+0x6424b9] G1EvacuateRegionsBaseTask::work(unsigned int)+0x99
V [libjvm.so+0xd8e23d] GangWorker::loop()+0x4d
V [libjvm.so+0xcf326d] Thread::call_run()+0xfd
V [libjvm.so+0xb468b7] thread_native_entry(Thread*)+0xe7


siginfo: si_signo: 11 (SIGSEGV), si_code: 1 (SEGV_MAPERR), si_addr: 0x00000000000000f0