When running jtreg test gc/TestAllocHumongousFragment.java#generational , the following Internal error was triggered :

# Internal Error (shenandoahVerifier.cpp:110), pid=68218, tid=68234
# Error: Before Full GC, Reachable; Object start should be within the region

Referenced from:
  interior location: 0x00000000c067b9fc
  0x00000000c067b9e8 - klass 0x000002ae00170dd0 [Ljava.lang.Object;
        allocated after mark start
    not after update watermark
        marked strong
        marked weak
    not in collection set
  age: 0
  mark: mark(is_unlocked no_hash age=0)
  region: | 12|R |O|BTE c0600000, c067ba80, c0680000|TAMS c0600000|UWM c067ba80|U 494K|T 0B|G 0B|P 0B|S 494K|L 494K|CP 0

Object:
  0x00000000fc900000 - safe print, no details
  region: | 1938|EC |F|BTE fc900000, fc900000, fc980000|TAMS fc900000|UWM fc900000|U 0B|T 0B|G 0B|P 0B|S 0B|L 0B|CP 0

Raw heap memory:
0x00000000fc900000: 00000001 00000000 00172210 0019bb53 ........."..S...
0x00000000fc900010: 00000000 00000000 00000000 00000000 ................
0x00000000fc900020: 00000000 00000000 00000000 00000000 ................
0x00000000fc900030: 00000000 00000000 00000000 00000000 ................
0x00000000fc900040: 00000000 00000000 00000000 00000000 ................
0x00000000fc900050: 00000000 00000000 00000000 00000000 ................
0x00000000fc900060: 00000000 00000000 00000000 00000000 ................
0x00000000fc900070: 00000000 00000000 00000000 00000000 ................

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x122be08] VMError::report(outputStream*, bool)+0x28a8 (shenandoahVerifier.cpp:110)
V [libjvm.so+0x1230b78] VMError::report_and_die(int, char const*, char const*, char*, Thread*, unsigned char*, void const*, void const*, char const*, int, unsigned long)+0x428 (vmError.cpp:1825)
V [libjvm.so+0x673c8c] report_vm_error(char const*, int, char const*, char const*, ...)+0xdc (debug.cpp:196)
V [libjvm.so+0x673ce0] report_vm_error(char const*, int, char const*)+0x30 (debug.cpp:149)
V [libjvm.so+0xf503e0] ShenandoahAsserts::print_failure(ShenandoahAsserts::SafeLevel, oopDesc*, void*, oopDesc*, char const*, char const*, char const*, int)+0x220 (shenandoahAsserts.cpp:168)
V [libjvm.so+0x105c058] ShenandoahVerifyOopClosure::verify_oop(oopDesc*)+0x618 (shenandoahVerifier.cpp:110)
V [libjvm.so+0x1063bd0] void OopOopIterateDispatch<ShenandoahVerifyOopClosure>::Table::oop_oop_iterate<ObjArrayKlass, narrowOop>(ShenandoahVerifyOopClosure*, oopDesc*, Klass*)+0x370 (shenandoahVerifier.cpp:332)
V [libjvm.so+0x105e160] ShenandoahVerifierReachableTask::work(unsigned int)+0x320 (iterator.inline.hpp:300)
V [libjvm.so+0x1278014] WorkerThread::run()+0xe4 (workerThread.cpp:69)
V [libjvm.so+0x116ae1c] Thread::call_run()+0xec (thread.cpp:231)
V [libjvm.so+0xe15040] thread_native_entry(Thread*)+0x130 (os_linux.cpp:875)
C [libc.so.6+0xb2014] start_thread+0x184

The issue was seen on Linux ppc64le. On Linux x86_64 we saw no such crash but quite a few timeouts when running this test.