The following test failed in the JDK16 CI:

vmTestbase/nsk/jvmti/scenarios/capability/CM01/cm01t002/TestDescription.java

Here's a snippet from the log file:

#section:main
----------messages:(4/287)----------
command: main -agentlib:cm01t002=-waittime=5 nsk.jvmti.scenarios.capability.CM01.cm01t002
reason: User specified action: run main/othervm/native -agentlib:cm01t002=-waittime=5 nsk.jvmti.scenarios.capability.CM01.cm01t002
Mode: othervm [/othervm specified]
elapsed time (seconds): 14.45
----------configuration:(0/0)----------
----------System.out:(18/1374)----------
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=/jniHandles.inline.hpp:91
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/System/Volumes/Data/mesos/work_dir/slaves/47535081-0322-4d83-bb78-f7e11abb86d0-S39152/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/752dd27d-cd18-47ea-a26d-bde72528acec/runs/cd1229c8-32af-45f9-be39-31dad75b86eb/workspace/open/src/hotspot/share/runtime/jniHandles.inline.hpp:91), pid=44306, tid=25351
# assert(handle != __null) failed: JNI handle should not be null
#
# JRE version: Java(TM) SE Runtime Environment (16.0+25) (fastdebug build 16-ea+25-1581)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 16-ea+25-1581, mixed mode, tiered, compressed oops, g1 gc, bsd-amd64)
# Core dump will be written. Default location: core.44306
#
# An error report file with more information is saved as:
# /scratch/mesos/slaves/47535081-0322-4d83-bb78-f7e11abb86d0-S1877/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/9968da67-bf2b-449c-844b-4e06bead38cd/runs/4467ddd8-753f-4d77-994d-ddf8b4fe3208/testoutput/test-support/jtreg_open_test_hotspot_jtreg_vmTestbase_nsk_jvmti/scratch/0/hs_err_pid44306.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(3/174)----------
java version "16-ea" 2021-03-16
Java(TM) SE Runtime Environment (fastdebug build 16-ea+25-1581)
Java HotSpot(TM) 64-Bit Server VM (fastdebug build 16-ea+25-1581, mixed mode)
----------rerun:(38/7635)*----------

Here's the crashing thread's stack:

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

Current thread (0x00007f7f0300bc20): JavaThread "JVMTI agent thread" daemon [_thread_in_vm, id=25351, stack(0x000070000da9a000,0x000070000db9a000)]

Stack: [0x000070000da9a000,0x000070000db9a000], sp=0x000070000db99950, free space=1022k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.dylib+0x114ea5d] VMError::report_and_die(int, char const*, char const*, __va_list_tag*, Thread*, unsigned char*, void*, void*, char const*, int, unsigned long)+0x6dd
V [libjvm.dylib+0x114f07b] VMError::report_and_die(Thread*, void*, char const*, int, char const*, char const*, __va_list_tag*)+0x3b
V [libjvm.dylib+0x60b9bf] report_vm_error(char const*, int, char const*, char const*, ...)+0x13f
V [libjvm.dylib+0x975903] jni_GetObjectClass+0x253
C [libcm01t002.dylib+0xafb2] agentProc(_jvmtiEnv*, JNIEnv_*, void*)+0x322
C [libcm01t002.dylib+0xca97] agentThreadWrapper(_jvmtiEnv*, JNIEnv_*, void*)+0x67
V [libjvm.dylib+0xbcfd0f] JvmtiAgentThread::start_function_wrapper(JavaThread*, Thread*)+0xcf
V [libjvm.dylib+0x10a80f4] JavaThread::thread_main_inner()+0x2b4
V [libjvm.dylib+0x10a3e17] Thread::call_run()+0x1b7
V [libjvm.dylib+0xe64b5f] thread_native_entry(Thread*)+0x15f
C [libsystem_pthread.dylib+0x3661] _pthread_body+0x154
C [libsystem_pthread.dylib+0x350d] _pthread_body+0x0
C [libsystem_pthread.dylib+0x2bf9] thread_start+0xd