IV67534: INCORRECT OPTIMIZATION IN JIT CAUSES APPLICATION ERROR

APAR status

• Closed as program error.

Error description

• Error Message: Our customer reported
  "java.lang.IllegalStateException: Timer already Cancelled"
  exception in their case. However, due to the nature of this
  problem, the error can manifest in many different ways, such as
  exception, crash, etc.
  .
  Stack Trace: java.lang.IllegalStateException:
  Timer already Cancelled.
      at java.util.Timer.sched(Timer.java:397)
      at java.util.Timer.schedule(Timer.java:193)
      at com.ibm.db2.jcc.am.Connection.scheduleQueryTimer(Connecti
  on.java:7988)
      at com.ibm.db2.jcc.am.po.a(po.java:5144)
      at com.ibm.db2.jcc.am.po.cc(po.java:5261)
  .
  

Local fix

• This issue can be worked around by using the
  -Xjit:disableLookahead option. Please note there will be some
  performance loss.
  

Problem summary

• One of the parts of the Class Lookahead optimization decides
  to remove a write to a field that is never explicitly read by
  the Java code (via a getfield bytecode).
  This can lead to two kinds of problems: (1) If the field
  is read by native code or indirectly via Reflection, it will
  appear uninitialized, and will contain a zero or null value;
  or (2) if the field was supposed to contain a reference to an
  object with a finalizer, then removing the write can cause that
  object to become unreachable, and the garbage collector can run
  its finalizer prematurely.
  

Problem conclusion

• The JIT has been updated to avoid removing field writes unless
  it is safe to do so.
  .
  This APAR will be fixed in the following Java Releases:
     7 R1 SR2  FP10 (7.1.2.10)
     7    SR8  FP10 (7.0.8.10)
     6 R1 SR8  FP3  (6.1.8.3)
     6    SR16 FP3  (6.0.16.3)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the 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

• R600 PSY

     UP

• R130 PSY

     UP