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IJ13395: JAVA JIT PPC: JIT HOLDING A COMPRESSED REFERENCE DURING A GC CYCLE

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APAR status

  • Closed as program error.

Error description

  • Error Message: SIGSEGV in JIT compiled code.
    .
    Stack Trace: N/A
    .
    The problem can result in a crash in JIT compiled code or a
    crash in the Garbage Collector.
    The problem can only occur on PPC platforms (AIX and LinuxPPC)
    and only when using compressed references. The problem therefore
    can not occur in 32bit JVMs or when using large enough heaps
    where compressed references are not possible.
    

Local fix

  • Prevent the JVM from using compressed references.
    -Xnocompressedrefs
    This option will have a performance penalty of around 10% in
    most cases.
    

Problem summary

  • The JIT could fail to generate a compressed reference decompress
    code sequence right after loading the compressed reference from
    a heap object field. This could allow for a GC opportunity to
    exist between the field load and the decompress. A GC cycle at
    this point could resulting in stale references which would cause
    a crash in the JIT or in a future GC cycle.
    

Problem conclusion

  • The JIT was modified such that a GC opportunity would force a
    pending decompress to be generated prior to the GC opportunity.
    .
    This APAR will be fixed in the following Java Releases:
       8    SR3 FP20  (8.0.3.20)
       7 R1 SR3 FP60  (7.1.3.60)
       7    SR9 FP60  (7.0.9.60)
    .
    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 number

    IJ13395

  • Reported component name

    JIT

  • Reported component ID

    620700124

  • Reported release

    130

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2019-02-08

  • Closed date

    2019-02-13

  • Last modified date

    2019-02-13

  • 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

[{"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SSNVBF","label":"Runtimes for Java Technology"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Line of Business":{"code":"LOB36","label":"IBM Automation"}}]

Document Information

Modified date:
14 December 2020