IJ48654: JAVA JIT: GC CRASH IN DOSTACKSLOT() ON POWER10

APAR status

• Closed as program error.

Error description

• Error Message: A SIGSEGV (Signal 11/0xB) during a GC cycle
  .
  Stack Trace:
  {libj9gc29.so}{_ZN23MM_ScavengerRootScanner11doStackSlotEPP8J9Ob
  jectPvPKv}
  {libj9gc29.so}{_Z17stackSlotIteratorP8J9JavaVMPP8J9ObjectPvP16J9
  StackWalkStatePKv}
  {libj9gc29.so}{vmThreadStackDoOSlotIterator}
  {libj9jit29.so}{jitWalkFrame}
  {libj9jit29.so}{jitWalkStackFrames}
  {libj9vm29.so}{walkStackFrames}
  {libj9gc29.so}{_ZN28GC_VMThreadStackSlotIterator9scanSlotsEP10J9
  VMThreadS1_PvPFvP8J9JavaVMPP8J9ObjectS2_P16J9StackWalkStatePKvEb
  b}
  {libj9gc29.so}{_ZN14MM_RootScanner13scanOneThreadEP18MM_Environm
  entBaseP10J9VMThreadPv}
  {libj9gc29.so}{_ZN14MM_RootScanner11scanThreadsEP18MM_Environmen
  tBase}
  {libj9gc29.so}{_ZN14MM_RootScanner9scanRootsEP18MM_EnvironmentBa
  se}
  {libj9gc29.so}{_ZN12MM_Scavenger24workThreadGarbageCollectEP22MM
  _EnvironmentStandard}
  {libj9gc29.so}{_ZN23MM_ParallelScavengeTask3runEP18MM_Environmen
  tBase}
  .
  The problem can only occur when running after a CRIU restore or
  when loading portable AOT code (i.e AOT code compiled from
  inside a Linux container). The issue requires that the JIT
  compiles portable code that is targeting a CPU that is less then
  POWER10 (currently portable code targets POWER8), and the
  machine loading the portable code must be running a POWER10 CPU.
  

Local fix

• The problem can be avoided by preventing the JVM from loading
  the portable code (for the AOT case anyhow), this can be
  accomplished by using the "-Xshareclasses:none" java command
  line argument which will effect startup time but should not
  effect steady state execution speed.
  The other option is to put the POWER10 machine in "compatibility
  mode" which will prevent the JVM from generating code targeting
  POWER10.
  

Problem summary

• With POWER10 there is a new instruction that the JIT makes use
  of to efficiently load 64bit constants. Prior to POWER10 the JIT
  would make use of a table of constants and dedicate a register
  to point as this table. With POWER10 we can free up that
  register and therefore make the register available for other
  uses. This difference between P10 and older POWER machines
  caused an incompatibility when executing portable code that is
  compiled for P8 mixed with normal JIT code compiled for P10.
  

Problem conclusion

• When compiling portable code the JIT will now save and restore
  the register that is dedicated for the table of constants
  pointer.
  https://github.com/eclipse-openj9/openj9/pull/17964
  .
  This APAR will be fixed in the following Releases:
  .
  IBM Semeru Runtimes
     11              11.0.21.0
     17              17.0.9.0
  IBM SDK, Java Technology Edition
     8    SR8 FP11  (8.0.8.11)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  maintenance can be found at:
             https://www.ibm.com/support/pages/java-sdk
  

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

  JIT

• Fixed component ID

  620700124

Applicable component levels