SIGSEGV in PackageEntry::purge_qualified_exports()

On behalf of Ekaterina Vergizova <katya@azul.com>:

The attached test crashes on Linux and Windows with OpenJDK 11.0.8 and the latest jdk11u-dev. Full hs_err log is attached.

#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f654f707701, pid=30872, tid=30879
#
# JRE version: OpenJDK Runtime Environment 18.9 (11.0.8+10) (build 11.0.8+10)
# Java VM: OpenJDK 64-Bit Server VM 18.9 (11.0.8+10, mixed mode, tiered, compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0xbdf701] PackageEntry::purge_qualified_exports()+0x131
#
# Core dump will be written. Default location: Core dumps may be processed with "/usr/share/apport/apport %p %s %c %d %P %E" (or dumping to /home/cat/work/core.30872)
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#

--------------- S U M M A R Y ------------

Command Line: Test

Host: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz, 4 cores, 7G, Ubuntu 18.04.4 LTS
Time: Mon Aug 17 14:38:38 2020 MSK elapsed time: 29 seconds (0d 0h 0m 29s)

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

Stack: [0x00007f65214fc000,0x00007f65215fc000], sp=0x00007f65215f9c80, free space=1015k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0xbdf701] PackageEntry::purge_qualified_exports()+0x131
V [libjvm.so+0xbdf79f] PackageEntryTable::purge_all_package_exports()+0x5f
V [libjvm.so+0x5b04b2] ClassLoaderDataGraph::do_unloading(bool)+0x172
V [libjvm.so+0xd22de5] SystemDictionary::do_unloading(GCTimer*, bool)+0x45
V [libjvm.so+0x75644e] G1ConcurrentMark::remark()+0x8be
V [libjvm.so+0xdd7e93] VM_CGC_Operation::doit()+0xc3
V [libjvm.so+0xdcfa4c] VM_Operation::evaluate()+0xec
V [libjvm.so+0xdd5e53] VMThread::evaluate_operation(VM_Operation*)+0xa3
V [libjvm.so+0xdd7487] VMThread::loop()+0x257
V [libjvm.so+0xdd7a0d] VMThread::run()+0x6d
V [libjvm.so+0xd64f2b] Thread::call_run()+0x6b
V [libjvm.so+0xbc67b8] thread_native_entry(Thread*)+0x128