IV77502: JAVA JIT: OBJECT CORRUPTION RESULTING IN A CRASH OR ASSERT IN GC

APAR status

• Closed as program error.

Error description

• Error Message: A crash executing Java code (interpreter or JIT
  compiled) or an assert or crash in GC are the most likely
  scenarios, but other symptoms are possible.
  .
  Stack Trace:
  .
  

Local fix

• -Xjit:disableEscapeAnalysis prevents this failure from
  occurring.  The magnitude of the resulting performance
  degradation varies depending on the nature of the application,
  but most will see less then 2% performance loss.
  

Problem summary

• The JIT compiler performs an "escape analysis" to determine
  whether an object escapes from a method, and if not, it can
  allocate that object in the method's stack frame.  This analysis
  contained a flaw that could occasionally cause an internal data
  structure to become truncated, which caused the analysis to stop
  before it had finished scanning for escape points.  This caused
  the analysis to miss an escape point, and so it stack-allocated
  an object that actually outlived the method invocation.  As a
  result, the object's memory was freed prematurely, as soon as
  the method returned, even though the object was still in use.
  

Problem conclusion

• The JIT compiler was fixed to keep the data structure in a
  consistent state throughout the escape analysis.
  .
  This APAR will be fixed in the following Java Releases:
     6 R1 SR8 FP15  (6.1.8.15)
     7 R1 SR3 FP20  (7.1.3.20)
     8    SR2       (8.0.2.0)
  .
  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

• R260 PSY

     UP

• R130 PSY

     UP