IV19966: NON-ATOMIC VARIABLE-LENGTH ARRAYSET

APAR status

• Closed as program error.

Error description

• Error Message: The following assertion in the GC was observed:
  0xf69800    j9mm.107    *   ** ASSERTION FAILED ** at
  MarkingScheme.cpp:299: ((isHeapObject(objectPtr)))
  .
  Stack Trace: N/A
  .
  

Local fix

• This issue can be avoided using the
  -Xjit:disableIdiomRecognition,disableSequentialStoreSimplificati
  on,disableLoopReduction option. This option may cause a
  noticeable performance degradation.
  

Problem summary

• The inlined sequence for variable-length non-byte arrayset
  generated by the Java JIT Compiler includes a single-byte XC
  instruction to handle residual (<256 bytes) elements.  As a
  result of this single byte clearing, a partially cleared and
  invalid element value may be visible to other threads
  concurrently examining that array.
  This issue only impacts JDKs on Linux on Z and zOS.
  

Problem conclusion

• This defect will be fixed in:
  6.0.1 SR2
  7.0.0 SR1
  .
  The JVM has been updated to remove the single-byte XC
  instruction and generate an atomic sequence for all arrayset.
  

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

• R260 PSY

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