The following test failed in the JDK16 CI:

applications/kitchensink/Kitchensink24HStress.java

Here's a snippet from the log file:

Iteration start: Allocator at Wed Jul 01 12:56:10 UTC 2020
Iteration start: MemAccess at Wed Jul 01 12:56:32 UTC 2020


The tail of stress stdout is:
For random generator using seed: -7486307213896385431
To re-run test with same seed value please add "-Djdk.test.lib.random.seed=-7486307213896385431" to command line.
Stress process main method is started.
[thread 8163 also had an error][thread 8164 also had an error]
[thread 8165 also had an error]
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f01d4f5cc82, pid=8099, tid=8166
#
# 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, jvmci, jvmci compiler, compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# C 0x00007f01d4f5cc82
#
# 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-S82/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/d4eed71b-30c8-4e77-90ac-6328fdeb9c44/runs/d4a52862-b8c9-4ad7-86cf-76cb6b8558c0/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_kitchensink_Kitchensink24HStress_java/scratch/0/core.8099)
#
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-S82/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/d4eed71b-30c8-4e77-90ac-6328fdeb9c44/runs/d4a52862-b8c9-4ad7-86cf-76cb6b8558c0/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_kitchensink_Kitchensink24HStress_java/scratch/0/hs_err_pid8099.log

[thread 8167 also had an error]
[thread 8161 also had an error]
[thread 8103 also had an error]
[thread 8162 also had an error]
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(223/21241)----------


Here's the crashing thread's stack:

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

Current thread (0x00007f01980071c0): GCTaskThread "GC Thread#6" [stack: 0x00007f01430ed000,0x00007f01431ed000] [id=8166]

Stack: [0x00007f01430ed000,0x00007f01431ed000], sp=0x00007f01431ebae8, free space=1018k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
C 0x00007f01d4f5cc82
V [libjvm.so+0x63377d] G1CodeRootSet::nmethods_do(CodeBlobClosure*) const+0x4d
V [libjvm.so+0x69ea2b] G1ScanCollectionSetRegionClosure::do_heap_region(HeapRegion*)+0xbb
V [libjvm.so+0x6458fd] G1CollectionSet::iterate_part_from(HeapRegionClosure*, HeapRegionClaimer*, unsigned long, unsigned long, unsigned int, unsigned int) const [clone .part.0]+0x13d
V [libjvm.so+0x645ff1] G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure*, HeapRegionClaimer*, unsigned int, unsigned int) const+0x21
V [libjvm.so+0x694457] G1RemSet::scan_collection_set_regions(G1ParScanThreadState*, unsigned int, G1GCPhaseTimes::GCParPhases, G1GCPhaseTimes::GCParPhases, G1GCPhaseTimes::GCParPhases)+0x87
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: 0x0000000000000006