SIGSEGV in Metadata::mark_on_stack() while marking metadata in ciEnv

#
# SIGSEGV (0xb) at pc=0x00007fad3e410cac, pid=105294, tid=140381245028096
#
# JRE version: OpenJDK Runtime Environment (9.0) (build 1.9.0-internal-vlivanov_2014_09_19_07_15-b00)
# Java VM: OpenJDK 64-Bit Server VM (1.9.0-internal-vlivanov_2014_09_19_07_15-b00 mixed mode linux-amd64 compressed oops)
# Problematic frame:
# V [libjvm.so+0x819cac] Metadata::mark_on_stack(Metadata*)+0xc

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x819cac] Metadata::mark_on_stack(Metadata*)+0xc
V [libjvm.so+0x41c857] ciObjectFactory::metadata_do(void (*)(Metadata*))+0x47
V [libjvm.so+0x9c5e6e] JavaThread::metadata_do(void (*)(Metadata*))+0x16e
V [libjvm.so+0x9c5eab] Threads::metadata_do(void (*)(Metadata*))+0x2b
V [libjvm.so+0x819bd8] MetadataOnStackMark::MetadataOnStackMark(bool)+0x28
V [libjvm.so+0x450034] ClassLoaderDataGraph::do_unloading(BoolObjectClosure*)+0x44
V [libjvm.so+0x992e38] SystemDictionary::do_unloading(BoolObjectClosure*)+0x18
V [libjvm.so+0x8ea0cf] PSParallelCompact::marking_phase(ParCompactionManager*, bool, ParallelOldTracer*)+0x53f
V [libjvm.so+0x8efa06] PSParallelCompact::invoke_no_policy(bool)+0x476
V [libjvm.so+0x8f02b4] PSParallelCompact::invoke(bool)+0x64
V [libjvm.so+0xa1c50e] VM_ParallelGCSystemGC::doit()+0x10e
V [libjvm.so+0xa22bf2] VM_Operation::evaluate()+0x52
V [libjvm.so+0xa21121] VMThread::evaluate_operation(VM_Operation*)+0xb1
V [libjvm.so+0xa21573] VMThread::loop()+0x1c3
V [libjvm.so+0xa21a42] VMThread::run()+0x72
V [libjvm.so+0x895642] java_start(Thread*)+0x122

VM_Operation (0x00007fad0c2507e0): ParallelGCSystemGC, mode: safepoint, requested by thread 0x00007fac20001000

How to reproduce:
  - apply 8060147.jdk.patch (attached); it stresses VM anonymous class unloading
  - run Octane:
     $ java -jar microbenchmarks.jar -f 0 '.*octane.Typescript.*' &
  - stress frequent full GCs:
     $ while sleep 1; do jcmd $! GC.run; done;