IJ32708: JAVA JIT SEGV IN DECREFERENCECOUNT() ON ZOS/ZLINUX WHILE JIT COMPILING

APAR status

• Closed as program error.

Error description

• Error Message: JIT: Fatal Crash in the JIT while compiling
  .
  Stack Trace:
  {libj9jit29.so}{OMR::CodeGenerator::decReferenceCount(TR::Node*)
  }
  {libj9jit29.so}{J9::Z::TreeEvaluator::pdloadEvaluator(TR::Node*,
  TR::CodeGenerator*)}
  {libj9jit29.so}{OMR::CodeGenerator::evaluate(TR::Node*)}
  {libj9jit29.so}{J9::Z::TreeEvaluator::pdstoreEvaluator(TR::Node*
  ,TR::CodeGenerator*)}
  {libj9jit29.so}{OMR::CodeGenerator::evaluate(TR::Node*)}
  {libj9jit29.so}{J9::CodeGenerator::doInstructionSelection()}
  {libj9jit29.so}{OMR::CodeGenPhase::performInstructionSelectionPh
  ase(TR::CodeGenerator*,TR::CodeGenPhase*)}
  {libj9jit29.so}{OMR::CodeGenPhase::performAll()}
  {libj9jit29.so}{OMR::CodeGenerator::generateCode()}
  {libj9jit29.so}{OMR::Compilation::compile()}
  .
  The problem can only occur on zOS and zLinux running the J9 JVM
  when using packed decimal variables. Typically this is done by
  Java code that makes use of the com.ibm.jzos package.
  The stack trace must include pdloadEvaluator() when this problem
  occurs.
  

Local fix

• The problem can be avoided by preventing the JIT from attempting
  to execute the loop version optimization against code that uses
  a packed decimal variables within a loop. Globally this can be
  achieved using the following Java command line option:
  -Xjit:disableLoopVersioner
  For a lower impact option you can disable loop versioner only
  for the java method where the problem had surfaced:
  -Xjit:{pkg/class.method*}(disableLoopVersioner)
  Where pkg/class.method is found in the console or javacore
  output like the following:
  1XHEXCPMODULE  Compiling method: pkg/class.method
  

Problem summary

• The JIT attempts to optimize loops by privatizing parts of the
  loop. When attempting to privatize packed decimal variables it
  would break some rules specific to packed decimal handling in
  the JIT.
  

Problem conclusion

• The JIT was changed so that the loop versioner will not attempt
  to privatize when it encounters packed decimal variables.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR6 FP35  (8.0.6.35)
  .
  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

  JIT

• Fixed component ID

  620700124

Applicable component levels