This is on behalf of <wattsun@tencent.com>.

* Symptom
---------------------
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/home/wattsun/source/jdk8u/hotspot/src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp:165), pid=7683, tid=0x00007f776242f700
# guarantee(!obj->is_forwarded()) failed: Object must not be forwarded
#


Current thread (0x00007f778753e000): VMThread [stack: 0x00007f776232f000,0x00007f7762430000] [id=7706]

Stack: [0x00007f776232f000,0x00007f7762430000], sp=0x00007f776242c4c0, free space=1013k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x10ea81d] VMError::report_and_die()+0x15d
V [libjvm.so+0x740d3b] report_vm_error(char const*, int, char const*, char const*)+0x7b
V [libjvm.so+0x88844f] G1StringDedupQueue::verify()+0x3df
V [libjvm.so+0x886d76] G1StringDedup::verify()+0x36
V [libjvm.so+0x83d746] G1CollectedHeap::verify(bool, VerifyOption) [clone .part.325]+0x556
V [libjvm.so+0x8762ad] G1MarkSweep::mark_sweep_phase1(bool&, bool)+0x31d
V [libjvm.so+0x876793] G1MarkSweep::invoke_at_safepoint(ReferenceProcessor*, bool)+0x143
V [libjvm.so+0x840192] G1CollectedHeap::do_collection(bool, bool, unsigned long)+0x722
V [libjvm.so+0x1114d14] VM_G1CollectFull::doit()+0xa4
V [libjvm.so+0x1113623] VM_Operation::evaluate()+0xa3
V [libjvm.so+0x111018a] VMThread::evaluate_operation(VM_Operation*)+0x18a
V [libjvm.so+0x1110bca] VMThread::loop()+0x4ea
V [libjvm.so+0x1110e98] VMThread::run()+0x108
V [libjvm.so+0xe30c92] java_start(Thread*)+0xf2

VM_Operation (0x00007f7789db0d80): G1CollectFull, mode: safepoint, requested by thread 0x00007f7787448800
---------------------


* Reproduce

java -Xmx10M -XX:+UnlockDiagnosticVMOptions -XX:+UseG1GC -XX:+VerifyDuringGC -XX:+UseStringDeduplication GCStringTest

---------------------
class GCStringTest {
    public static void main(String [] args) {
      String str = new Integer(10).toString();
      System.gc();
    }
}
---------------------