gc/stress/TestStressRSetCoarsening.java hits assert assert(ILocked()) failed: invariant

# Internal Error (hotspot/src/share/vm/runtime/mutex.cpp:459), pid=30320, tid=30333
# assert(ILocked()) failed: invariantCurrent thread (0x0000007f8404d000): ConcurrentGCThread "G1 Refine#6" [stack: 0x0000007f4fbfe000,0x0000007f4fcfe000] [id=30333]

Stack: [0x0000007f4fbfe000,0x0000007f4fcfe000], sp=0x0000007f4fcfbf70, free space=1015k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x108c878] VMError::report(outputStream*, bool)+0x1780
V [libjvm.so+0x108ce60] VMError::report_and_die(int, char const*, char const*, std::__va_list, Thread*, unsigned char*, void*, void*, char const*, int, unsigned long)+0x140
V [libjvm.so+0x108da70] VMError::report_and_die(Thread*, char const*, int, char const*, char const*, std::__va_list)+0x54
V [libjvm.so+0x6b51ac] report_vm_error(char const*, int, char const*, char const*, ...)+0xe0
V [libjvm.so+0xd54944] Monitor::ILock(Thread*)+0x114
V [libjvm.so+0xd570c4] Monitor::lock_without_safepoint_check()+0x54
V [libjvm.so+0x8ee060] OtherRegionsTable::add_reference(void*, unsigned int)+0x170
V [libjvm.so+0x81bda4] void G1UpdateRSOrPushRefOopClosure::do_oop_work<unsigned int>(unsigned int*)+0x1a0
V [libjvm.so+0x7fa07c] ObjArrayKlass::oop_oop_iterate_bounded_nv(oop, FilterOutOfRegionClosure*, MemRegion)+0x198
V [libjvm.so+0x8e0954] HeapRegion::oops_on_card_seq_iterate_careful(MemRegion, FilterOutOfRegionClosure*, bool, signed char*)+0x79c
V [libjvm.so+0x8195d4] G1RemSet::refine_card(signed char*, unsigned int, G1ParPushHeapRSClosure*)+0x200
V [libjvm.so+0x7b7064] RefineCardTableEntryClosure::do_card_ptr(signed char*, unsigned int)+0x38
V [libjvm.so+0x736910] DirtyCardQueueSet::apply_closure_to_buffer(CardTableEntryClosure*, BufferNode*, bool, unsigned int)+0xa4
V [libjvm.so+0x736e30] DirtyCardQueueSet::apply_closure_to_completed_buffer(CardTableEntryClosure*, unsigned int, unsigned long, bool)+0x9c
V [libjvm.so+0x661808] ConcurrentG1RefineThread::run_service()+0x14c
V [libjvm.so+0x662100] ConcurrentGCThread::run()+0x98
V [libjvm.so+0xdc45d8] thread_native_entry(Thread*)+0x118
C [libpthread.so.0+0x7e2c] start_thread+0xb0