The following test failed in the JDK16 CI:

applications/dacapo/Dacapo24H.java

Here's a snippet from the log file:

Stress process main method is started.
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f082879079f, pid=9884, tid=9895
#
# JRE version: Java(TM) SE Runtime Environment (16.0+17) (build 16-ea+17-753)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (16-ea+17-753, mixed mode, sharing, tiered, jvmci, jvmci compiler, compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0xd1479f] DeadlockCycle::print_on_with(ThreadsList*, outputStream*) const+0x9f
#
# 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/4076d11c-c6ed-4d07-84c1-4ab8d55cd975-S108838/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/eb71e294-f158-43a6-a551-e0d73cefef61/runs/6eb6359d-8b7c-4198-ba29-70ec1ce4fd8e/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_dacapo_Dacapo24H_java/scratch/0/core.9884)
#
Unsupported internal testing APIs have been used.

# An error report file with more information is saved as:
# /opt/mach5/mesos/work_dir/slaves/4076d11c-c6ed-4d07-84c1-4ab8d55cd975-S108838/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/eb71e294-f158-43a6-a551-e0d73cefef61/runs/6eb6359d-8b7c-4198-ba29-70ec1ce4fd8e/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_dacapo_Dacapo24H_java/scratch/0/hs_err_pid9884.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(130/13834)----------

Here's the crashing thread's stack:

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

Current thread (0x00007f0820178800): VMThread "VM Thread" [stack: 0x00007f07d1700000,0x00007f07d1800000] [id=9895]

Stack: [0x00007f07d1700000,0x00007f07d1800000], sp=0x00007f07d17fe9d0, 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+0xd1479f] DeadlockCycle::print_on_with(ThreadsList*, outputStream*) const+0x9f
V [libjvm.so+0xd795be] VM_FindDeadlocks::doit()+0x5e
V [libjvm.so+0xd79b2a] VM_Operation::evaluate()+0xea
V [libjvm.so+0xd7b4d5] VMThread::evaluate_operation(VM_Operation*)+0xb5
V [libjvm.so+0xd7bae9] VMThread::loop()+0x3a9
V [libjvm.so+0xd7bc78] VMThread::run()+0x78
V [libjvm.so+0xd07f3d] Thread::call_run()+0xfd
V [libjvm.so+0xb5b837] thread_native_entry(Thread*)+0xe7


siginfo: si_signo: 11 (SIGSEGV), si_code: 128 (SI_KERNEL), si_addr: 0x0000000000000000


I'm starting this bug off in hotspot/runtime for initial triage.
The crash is in the VMThread's call to DeadlockCycle::print_on_with()
due to a NULL pointer deref based on:

siginfo: si_signo: 11 (SIGSEGV), si_code: 128 (SI_KERNEL), si_addr: 0x0000000000000000

Although the SI_KERNEL part might be related to something else.
I have a vague memory, but I can't pull it up...