The following test failed in the JDK16 CI:

applications/kitchensink/Kitchensink.java

Here's a snippet from the log file:

Iteration done: ThreadDumper at Sat Jun 27 19:42:13 UTC 2020
Iteration start: LockDeflation at Sat Jun 27 19:42:18 UTC 2020
Iteration done: SpecJbb2005 at Sat Jun 27 19:42:23 UTC 2020
Iteration start: SpecJbb2005 at Sat Jun 27 19:42:23 UTC 2020
Iteration done: LockDeflation at Sat Jun 27 19:42:56 UTC 2020
Iteration start: MemAccess at Sat Jun 27 19:43:11 UTC 2020
Iteration done: Allocator at Sat Jun 27 19:43:15 UTC 2020
Iteration start: Allocator at Sat Jun 27 19:43:15 UTC 2020
Iteration done: MemAccess at Sat Jun 27 19:44:11 UTC 2020
Compiled method (c2) 455862 19152 ! 4 sun.nio.ch.FileChannelImpl$Closer::run (28 bytes)
 total in heap [0x00007fa12da66410,0x00007fa12da678b0] = 5280
 relocation [0x00007fa12da66568,0x00007fa12da665a0] = 56
 main code [0x00007fa12da665a0,0x00007fa12da66f20] = 2432
 stub code [0x00007fa12da66f20,0x00007fa12da66f48] = 40
 oops [0x00007fa12da66f48,0x00007fa12da66f50] = 8
 metadata [0x00007fa12da66f50,0x00007fa12da66f90] = 64
 scopes data [0x00007fa12da66f90,0x00007fa12da671d0] = 576
 scopes pcs [0x00007fa12da671d0,0x00007fa12da67880] = 1712
 dependencies [0x00007fa12da67880,0x00007fa12da67898] = 24
 handler table [0x00007fa12da67898,0x00007fa12da678b0] = 24


The tail of stress stdout is:
For random generator using seed: 4976682410192462535
To re-run test with same seed value please add "-Djdk.test.lib.random.seed=4976682410192462535" to command line.
Stress process main method is started.
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007fa14303b8ab, pid=4717, tid=4729
#
# JRE version: Java(TM) SE Runtime Environment (16.0+4) (build 16-ea+4-98)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (16-ea+4-98, mixed mode, sharing, tiered, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0xb208ab] ObjectMonitor::enter(Thread*)+0x26b
#
# 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-S227/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/a9a4e078-02f5-4b44-9e6a-a89c7624241e/runs/c44a811c-a50d-40ae-840f-5ebd561d98ba/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_kitchensink_Kitchensink_java/scratch/0/core.4717)
#
# JFR recording file will be written. Location: /opt/mach5/mesos/work_dir/slaves/4728e7c1-7e67-490e-be0f-6bbf2a2f33db-S227/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/a9a4e078-02f5-4b44-9e6a-a89c7624241e/runs/c44a811c-a50d-40ae-840f-5ebd561d98ba/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_kitchensink_Kitchensink_java/scratch/0/hs_err_pid4717.jfr
#
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-S227/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/a9a4e078-02f5-4b44-9e6a-a89c7624241e/runs/c44a811c-a50d-40ae-840f-5ebd561d98ba/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_kitchensink_Kitchensink_java/scratch/0/hs_err_pid4717.log
[thread 11945 also had an error]
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(178/17466)----------


Here's the crashing thread's stack:

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

Current thread (0x00007fa13c1ac0c0): JavaThread "Finalizer" daemon [_thread_in_vm, id=4729, stack(0x00007fa124a1d000,0x00007fa124b1e000)]

Stack: [0x00007fa124a1d000,0x00007fa124b1e000], sp=0x00007fa124b1c7d0, free space=1021k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0xb208ab] ObjectMonitor::enter(Thread*)+0x26b
V [libjvm.so+0xc98c6c] ObjectSynchronizer::enter(Handle, BasicLock*, Thread*)+0xcc
V [libjvm.so+0xbf96f0] SharedRuntime::complete_monitor_locking_C(oopDesc*, BasicLock*, JavaThread*)+0x60

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
v ~RuntimeStub::_complete_monitor_locking_Java
J 20526 c2 jdk.nio.zipfs.ZipFileSystem.close()V jdk.zipfs@16-ea (390 bytes) @ 0x00007fa12da331cc [0x00007fa12da30f60+0x000000000000226c]
J 52828 c2 jdk.nio.zipfs.ZipFileSystem.finalize()V jdk.zipfs@16-ea (5 bytes) @ 0x00007fa12c9c7db4 [0x00007fa12c9c7d80+0x0000000000000034]
J 45517% c2 java.lang.ref.Finalizer$FinalizerThread.run()V java.base@16-ea (56 bytes) @ 0x00007fa12e458420 [0x00007fa12e457e60+0x00000000000005c0]
v ~StubRoutines::call_stub

siginfo: si_signo: 11 (SIGSEGV), si_code: 1 (SEGV_MAPERR), si_addr: 0x00000000000001af