jdk9 b107 PIT testing
seen only once:

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/scratch/opt/jprt/T/P1/215959.amurillo/s/hotspot/src/share/vm/gc/shared/gcTimer.cpp:88), pid=901, tid=926
# assert(_is_concurrent_phase_active) failed: A concurrent phase is not active.
#
# JRE version: Java(TM) SE Runtime Environment (9.0) (fastdebug build 9-internal+0-2016-02-11-215959.amurillo.jdk9-hs-2016-02-11-snapshot)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 9-internal+0-2016-02-11-215959.amurillo.jdk9-hs-2016-02-11-snapshot, compiled mode, tiered, compressed oops, g1 gc, linux-amd64)
# Core dump will be written. Default location: Core dumps may be processed with "/usr/share/apport/apport %p %s %c" (or dumping to /export/local/aurora/sandbox/results/ResultDir/jck90002_copy_1/core.901)
#
# If you would like to submit a bug report, please visit:
# http://bugreport.java.com/bugreport/crash.jsp
#

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

Command Line: -Xcomp -XX:+CreateCoredumpOnCrash -XX:+IgnoreUnrecognizedVMOptions -XX:ReservedCodeCacheSize=256M -Xcomp -Xverify:all -XX:MaxMetaspaceSize=128m -XX:CompressedClassSpaceSize=64m -XX:MaxHeapSize=512m -XX:+IgnoreUnrecognizedVMOptions -XX:+PrintHeapAtGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -Xlog:gc* nsk.stress.share.MetaspaceTestRunner -testList /export/local/aurora/CommonData/vm/src/nsk/stress/jck90/jck90002/tests

Host: jtg-x2200-04, Dual-Core AMD Opteron(tm) Processor 2220, 4 cores, 7G, Ubuntu 12.10
Time: Sat Feb 13 12:09:20 2016 PST elapsed time: 825 seconds (0d 0h 13m 45s)

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

Current thread (0x00007fb1541d2800): VMThread [stack: 0x00007fb13c066000,0x00007fb13c167000] [id=926]

Stack: [0x00007fb13c066000,0x00007fb13c167000], sp=0x00007fb13c1654a0, free space=1021k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x13db7e2] VMError::report_and_die(int, char const*, char const*, __va_list_tag*, Thread*, unsigned char*, void*, void*, char const*, int, unsigned long)+0x162
V [libjvm.so+0x13dc4bf] VMError::report_and_die(Thread*, char const*, int, char const*, char const*, __va_list_tag*)+0x2f
V [libjvm.so+0x93f35d] report_vm_error(char const*, int, char const*, char const*, ...)+0xdd
V [libjvm.so+0xb2795c] ConcurrentGCTimer::register_gc_concurrent_end(Ticks const&)+0x3c
V [libjvm.so+0xaae618] G1ConcurrentMark::abort()+0x118
V [libjvm.so+0xa8fc6f] G1CollectedHeap::do_full_collection(bool, bool)+0x47f
V [libjvm.so+0x881ea1] CollectedHeap::collect_as_vm_thread(GCCause::Cause)+0x231
V [libjvm.so+0x13dd711] VM_CollectForMetadataAllocation::doit()+0x221
V [libjvm.so+0x140d7d4] VM_Operation::evaluate()+0xb4
V [libjvm.so+0x140ac72] VMThread::evaluate_operation(VM_Operation*)+0x162
V [libjvm.so+0x140b3c6] VMThread::loop()+0x236
V [libjvm.so+0x140b933] VMThread::run()+0xb3
V [libjvm.so+0x10ca582] java_start(Thread*)+0xd2

VM_Operation (0x00007fb0bbffcbf0): CollectForMetadataAllocation, mode: safepoint, requested by thread 0x00007fb155cbd000