IJ44532: JAVA JIT: CRASH IN DECREFERENCECOUNT() DUE TO A NULL POINTER

APAR status

• Closed as program error.

Error description

• Error Message: A segmentation fault in the JIT compiler (compile
  time).
  .
  Stack Trace: libj9jit29.so -
  OMR::CodeGenerator::decReferenceCount(TR::Node*)}
  libj9jit29.so -
  J9::Z::TreeEvaluator::pdloadEvaluator(TR::Node*,TR::CodeGenerato
  r*)}
  libj9jit29.so - OMR::CodeGenerator::evaluate(TR::Node*)}
  libj9jit29.so -
  J9::Z::TreeEvaluator::pdstoreEvaluator(TR::Node*,TR::CodeGenerat
  or*)}
  libj9jit29.so -
  J9::Z::TreeEvaluator::pdstoreiEvaluator(TR::Node*,TR::CodeGenera
  tor*)}
  libj9jit29.so - OMR::CodeGenerator::evaluate(TR::Node*)}
  libj9jit29.so - J9::CodeGenerator::doInstructionSelection()}
  libj9jit29.so -
  OMR::CodeGenPhase::performInstructionSelectionPhase(TR::CodeGene
  rator*,TR::CodeGenPhase*)}
  libj9jit29.so - OMR::CodeGenPhase::performAll()}
  libj9jit29.so - OMR::CodeGenerator::generateCode()}
  libj9jit29.so - OMR::Compilation::compile()}
  libj9jit29.so -
  TR::CompilationInfoPerThreadBase::compile(J9VMThread*,TR::Compil
  ation*,TR_ResolvedMethod*,T...}
  libj9jit29.so -
  TR::CompilationInfoPerThreadBase::wrappedCompile(J9PortLibrary*,
  void*)}
  .
  The problem can only occur running the zSeries IBM JVM on a z15
  or newer CPU. Other (non-z) CPU architectures are not effect by
  this issue. The issue only occurs when the Java application is
  making use of the IBM Data Access Accelerator Library (DAA) to
  manipulate packed decimal values.
  

Local fix

• The problem can be avoided by specifying the following java
  command line argument:
  -Xjit:disableVectorBCD
  This will have some performance effect on methods that are
  making use of the DAA API.
  The following environment variable can be used instead if
  performance is a concern. Using this environment variable is
  more targeted to the specific issue and will therefore have less
  of a performance impact:
  TR_DisablePdstoreVectorEvaluator=1
  

Problem summary

• Under some scenarios when compiling methods with DAA code, the
  JIT will call decReferenceCount() against a null pointer
  resulting in a segmentation fault.
  

Problem conclusion

• The JIT was modified so that it does not call
  decReferenceCount() under scenarios where the pdload operations
  are being evaluated.
  https://github.com/eclipse-openj9/openj9/pull/16287
  .
  This APAR will be fixed in the following Releases:
  .
  IBM SDK, Java Technology Edition
     8    SR8       (8.0.8.0)
  .
  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