The following test failed in the JDK16 CI:

runtime/logging/MonitorInflationTest.java

Here's a snippet from the log file:

----------System.err:(55/3449)*----------
 stdout: [[0.003s][warning][arguments] -XX:+TraceMonitorInflation is deprecated. Will use -Xlog:monitorinflation=trace instead.
[0.333s][trace ][monitorinflation] inflate(has_locker): object=0x000000047b8a0ea8, mark=0x0000023cff7e3532, type='MonitorInflationTest$Waiter'
I've been waiting.
[0.448s][trace ][monitorinflation] Checking in_use_list:
[0.448s][trace ][monitorinflation] count=1, max=1
[0.448s][trace ][monitorinflation] in_use_count=1 equals ck_in_use_count=1
[0.448s][trace ][monitorinflation] in_use_max=1 equals ck_in_use_max=1
[0.448s][trace ][monitorinflation] No errors found in in_use_list checks.
[0.448s][trace ][monitorinflation] In-use monitor info:
[0.448s][trace ][monitorinflation] (B -> is_busy, H -> has hash code, L -> lock status)
[0.448s][trace ][monitorinflation] monitor BHL object object type
[0.448s][trace ][monitorinflation] ================== === ================== ==================
[0.448s][trace ][monitorinflation] 0x0000023cff7e3530 000 0x000000047b8a0ea8 MonitorInflationTest$Waiter
[0.484s][debug ][monitorinflation] begin deflating: in_use_list stats: ceiling=11264, count=1, max=1
[0.484s][trace ][monitorinflation] deflate_monitor: object=0x000000047b8a0ea8, mark=0x0000023cff7e3532, type='MonitorInflationTest$Waiter'
[0.484s][debug ][monitorinflation] deflated 1 monitors in 0.0000488 secs
[0.484s][debug ][monitorinflation] end deflating: in_use_list stats: ceiling=11264, count=0, max=1
[0.484s][debug ][monitorinflation] begin deflating: in_use_list stats: ceiling=11264, count=0, max=1
#
# A fatal error has been detected by the Java Runtime Environment:
#
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00007ffa7d72eb60, pid=259220, tid=366152
#
# JRE version: Java(TM) SE Runtime Environment (16.0+27) (fastdebug build 16-ea+27-1844)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 16-ea+27-1844, mixed mode, sharing, tiered, compressed oops, g1 gc, windows-amd64)
# Problematic frame:
# V [jvm.dll+0xc4eb60] MonitorList::unlink_deflated+0x50
#
# Core dump will be written. Default location: T:\\testoutput\\test-support\\jtreg_open_test_hotspot_jtreg_tier1_runtime\\scratch\\3\\hs_err_pid259220.mdmp
#
# An error report file with more information is saved as:
# T:\\testoutput\\test-support\\jtreg_open_test_hotspot_jtreg_tier1_runtime\\scratch\\3\\hs_err_pid259220.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
];

Here's the crashing thread's stack:

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

Current thread (0x0000023cff7d5170): VMThread "VM Thread" [stack: 0x000000a35c400000,0x000000a35c500000] [id=366152]

Stack: [0x000000a35c400000,0x000000a35c500000], sp=0x000000a35c4ff330, free space=1020k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xc4eb60] MonitorList::unlink_deflated+0x50 (synchronizer.cpp:116)
V [jvm.dll+0xc4be81] ObjectSynchronizer::deflate_idle_monitors+0x301 (synchronizer.cpp:1528)
V [jvm.dll+0xc4c2ed] ObjectSynchronizer::do_final_audit_and_print_stats+0xad (synchronizer.cpp:1673)
V [jvm.dll+0xd2256f] VMThread::run+0x26f (vmThread.cpp:204)
V [jvm.dll+0xc99824] Thread::call_run+0x1b4 (thread.cpp:398)
V [jvm.dll+0xaeb76e] thread_native_entry+0x10e (os_windows.cpp:561)
C [ucrtbase.dll+0x1fb80]
C [KERNEL32.DLL+0x84d4]
C [ntdll.dll+0x6e871]


siginfo: EXCEPTION_ACCESS_VIOLATION (0xc0000005), reading address 0x00000000000000c0