I reproduce this running gc/shenandoah/TestAllocIntArrays.java with -Xcomp but also saw it with:

gc/shenandoah/TestAllocIntArrays.java
gc/shenandoah/TestAllocObjectArrays.java
gc/shenandoah/TestAllocObjects.java
gc/shenandoah/TestJcmdHeapDump.java
gc/shenandoah/TestLotsOfCycles.java
gc/shenandoah/TestRetainObjects.java
gc/shenandoah/TestSieveObjects.java
gc/stress/gcbasher/TestGCBasherWithShenandoah.java

# Internal Error (/home/roland/jdk-jdk/src/hotspot/share/runtime/mutex.cpp:444), pid=1451666, tid=1451682
# assert(false) failed: Attempting to acquire lock ShenandoahAllocFailureGC_lock/safepoint out of order with lock MultiArray_lock/safepoint -- possible deadlock