Uploaded image for project: 'JDK'
  1. JDK
  2. JDK-8256040

Shenandoah: Allow NULL referent in ShenandoahReferenceProcessor::should_discover()

    XMLWordPrintable

    Details

    • Subcomponent:
      gc
    • Resolved In Build:
      b24
    • CPU:
      generic
    • OS:
      generic

      Description

      Testing showed the following assert:

      # Internal Error (/home/rkennke/src/openjdk/jdk/src/hotspot/share/oops/compressedOops.inline.hpp:54), pid=711923, tid=712264
      # assert(!is_null(v)) failed: narrow oop value can never be zero

      V [libjvm.so+0x1629c84] bool ShenandoahReferenceProcessor::should_discover<narrowOop>(oop, ReferenceType) const+0x404
      V [libjvm.so+0x162a01b] bool ShenandoahReferenceProcessor::discover<narrowOop>(oop, ReferenceType, unsigned int)+0x4b
      V [libjvm.so+0x16239e8] ShenandoahReferenceProcessor::discover_reference(oop, ReferenceType)+0x138
      V [libjvm.so+0x15b7a26] bool InstanceRefKlass::try_discover<narrowOop, ShenandoahMarkRefsMetadataClosure>(oop, ReferenceType, ShenandoahMarkRefsMetadataClosure*)+0x96
      V [libjvm.so+0x15b7b3d] void InstanceRefKlass::oop_oop_iterate_discovery<narrowOop, ShenandoahMarkRefsMetadataClosure, AlwaysContains>(oop, ReferenceType, ShenandoahMarkRefsMetadataClosure*, AlwaysContains&) [clone .constprop.696]+0x3d
      V [libjvm.so+0x15b7ce1] void InstanceRefKlass::oop_oop_iterate_ref_processing<narrowOop, ShenandoahMarkRefsMetadataClosure, AlwaysContains>(oop, ShenandoahMarkRefsMetadataClosure*, AlwaysContains&)+0x81
      V [libjvm.so+0x15b835e] void OopOopIterateDispatch<ShenandoahMarkRefsMetadataClosure>::Table::oop_oop_iterate<InstanceRefKlass, narrowOop>(ShenandoahMarkRefsMetadataClosure*, oop, Klass*)+0x1ee
      V [libjvm.so+0x15a905e] void ShenandoahConcurrentMark::do_task<ShenandoahMarkRefsMetadataClosure>(Padded<BufferedOverflowTaskQueue<ShenandoahMarkTask, (MEMFLAGS)5, 131072u>, 128ul>*, ShenandoahMarkRefsMetadataClosure*, unsigned short*, ShenandoahMarkTask*)+0x7be
      V [libjvm.so+0x15ab81e] void ShenandoahConcurrentMark::mark_loop_work<ShenandoahMarkRefsMetadataClosure, true>(ShenandoahMarkRefsMetadataClosure*, unsigned short*, unsigned int, TaskTerminator*)+0x3ce

      We have this code in ShRefProc::should_discover():
        oop referent = CompressedOops::decode_not_null(heap_oop);

      However, the referent can legally be NULL. We even treat NULL specially in is_inactive().

        Attachments

          Issue Links

            Activity

              People

              Assignee:
              rkennke Roman Kennke
              Reporter:
              rkennke Roman Kennke
              Votes:
              0 Vote for this issue
              Watchers:
              3 Start watching this issue

                Dates

                Created:
                Updated:
                Resolved: