IV81275: CRASH IN 4-BIT SHIFT COMPRESSED REFERENCES JVM WITH -XGCPOLICY:B ALANCED BECAUSE OF WRONG INTERNAL ALIGNMENT IN HYBRID DISCONTIGU

APAR status

• Closed as program error.

Error description

• Error Message: A SIGSEGV/GPF is received
  .
  Stack Trace: #13 <signal handler called>
  #14 0x00007ff19ccf09b6 in
  MM_GlobalMarkingScheme::scanObject(MM_EnvironmentVLHGC*,
  J9Object*, MM_GlobalMarkingScheme::ScanReason) ()
     from <SDK>/jre/lib/amd64/compressedr
  efs/libj9gc28.so
  #15 0x00007ff19ccf1443 in
  MM_GlobalMarkingScheme::markLiveObjectsScan(MM_EnvironmentVLHGC*
  ) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #16 0x00007ff19ccf1604 in
  MM_ParallelGlobalMarkTask::run(MM_EnvironmentBase*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #17 0x00007ff19cd10020 in
  MM_Dispatcher::run(MM_EnvironmentBase*, MM_Task*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #18 0x00007ff19cce8ad1 in
  MM_GlobalMarkDelegate::markAll(MM_EnvironmentVLHGC*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #19 0x00007ff19cce9a6d in
  MM_GlobalMarkDelegate::performMarkForGlobalGC(MM_EnvironmentVLHG
  C*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #20 0x00007ff19cc3cb4c in
  MM_IncrementalGenerationalGC::globalMarkPhase(MM_EnvironmentVLHG
  C*, bool) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #21 0x00007ff19cc3db01 in
  MM_IncrementalGenerationalGC::runGlobalGarbageCollection(MM_Envi
  ronmentVLHGC*, MM_AllocateDescription*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #22 0x00007ff19cc3e6c9 in
  MM_IncrementalGenerationalGC::masterThreadGarbageCollect(MM_Envi
  ronmentVLHGC*, MM_AllocateDescription*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #23 0x00007ff19cc4662e in
  MM_MasterGCThread::masterThreadEntryPoint() ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #24 0x00007ff19cc468fc in
  MM_MasterGCThread::master_thread_proc2(J9PortLibrary*, void*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  #25 0x00007ff19ebcbe05 in j9sig_protect () from
  <PATH>/jre/lib/amd64/compressedrefs/libj9prt28.so
  #26 0x00007ff19cc45af3 in
  MM_MasterGCThread::master_thread_proc(void*) ()
     from <PATH>/jre/lib/amd64/compressedrefs/libj9gc28.so
  .
  Occur with -Xgcpolicy:balanced only. InaccessibleAddress points
  to the beginning of one of object heap regions.
  

Local fix

• Do not use -Xgcpolicy:balanced with heaps larger then 28G (4-bit
  shift) with Compressed References JVM. Use smaller heap if
  possible. Use different GC policy or Full 64-bit JVM.
  

Problem summary

• An attempt to use Indexable Object (Array) larger then 16M with
  Compressed References JVM with heap larger then 28G and
  -Xgcpolicy:balanced can be a cause of crash in GC. The reason
  for this is possible wrong internal alignment inside Hybrid
  Discontiguous Array.
  

Problem conclusion

• An implementation for Hybrid Discontiguous Array has been
  corrected.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR3       (8.0.3.0)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  J9 COMMON CODE

• Fixed component ID

  620700127

Applicable component levels

• R270 PSY

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