==# JRE version: Java(TM) SE Runtime Environment (8.0_121-b31) (build 1.8.0_121-b31)
  # Java VM: Java HotSpot(TM) 64-Bit Server VM (25.121-b31 mixed mode linux-amd64 compressed oops)
  ==Current thread (0x00007f5d7c072000): ConcurrentGCThread [stack: 0x00007f5d0feff000,0x00007f5d10000000] [id=10314]

  ==Top native frames (up to 5):
V [libjvm.so+0x4c8d8b] oopDesc::size()+0x2b
V [libjvm.so+0x4cad10] CMTask::make_reference_grey(oopDesc*, HeapRegion*)+0xc0
V [libjvm.so+0x70e08a] JNIHandleBlock::oops_do(OopClosure*)+0x6a
V [libjvm.so+0x469060] ClassLoaderData::oops_do(OopClosure*, KlassClosure*, bool)+0x70
V [libjvm.so+0x63e2bf] InstanceClassLoaderKlass::oop_oop_iterate_nv(oopDesc*, G1CMOopClosure*)+0x3f

Looks like
JDK-8168914 Crash in ClassLoaderData/JNIHandleBlock::oops_do during
concurrent marking