IZ81067: JAVA JIT: HANG WHILE THE JIT IS COMPILING A METHOD.

APAR status

• Closed as program error.

Error description

• Error Message: The Java process hangs.
  .
  Stack Trace: One of the executing thread will have the following
  stack trace when the hang occurs:
  {libj9jit24.so}{removeRedundantMonitors__21TR_MonitorElimination
  Fv}
  {libj9jit24.so}{perform__21TR_MonitorEliminationFv}
  {libj9jit24.so}{IPRA.$performOptimization__16TR_OptimizerImplFPQ
  2_16TR_OptimizerImpl12OptimizationiN22}
  {libj9jit24.so}{IPRA.$performOptimization__16TR_OptimizerImplFPQ
  2_16TR_OptimizerImpl12OptimizationiN22}
  {libj9jit24.so}{optimize__16TR_OptimizerImplFv}
  {libj9jit24.so}{performOptimizations__14TR_CompilationFv}
  {libj9jit24.so}{compile__14TR_CompilationFv}
  {libj9jit24.so}{compile__18TR_CompilationInfoFP10J9VMThreadP14TR
  _CompilationP10TR_OptionsP17TR_ResolvedMethodR11TR_FrontEndP19TR
  _OptimizationPlan}
  {libj9jit24.so}{wrappedCompile__18TR_CompilationInfoFP13J9PortLi
  braryPQ2_18TR_CompilationInfo17CompileParameters}
  {libj9prt24.so}{j9sig_protect}
  {libj9jit24.so}{compile__18TR_CompilationInfoFP10J9VMThreadP21TR
  _MethodToBeCompiledb}
  {libj9jit24.so}{protectedCompilationThreadProc__FP13J9PortLibrar
  yPv}
  {libj9prt24.so}{j9sig_protect}
  {libj9jit24.so}{compilationThreadProc__FPv}
  {libj9thr24.so}{thread_wrapper}
  {libpthreads.a}{_pthread_body}
  .
  The problem can only occur with a large number of synchronized
  blocks. They can be synchronized blocks in the Java code or the
  result of the JIT inlining synchronized methods. The code
  between the blocks must be small so that the JIT will see a
  sync-exit with a sync-enter near by.
  

Local fix

• Using the following JIT options on the Java command line will
  avoid the problem:
  -Xjit:disableRedundantMonitorElimination
  Using this option my have a impact on performance, but it is
  expected to be a small impact unless monitors are used very
  frequently and a number of them are redundant.
  

Problem summary

• The JIT would spend a lot of time analysing synchronized blocks
  looking for opportunities to remove synchronization. This was
  caused by a large number of synchronized block being examined
  repeatedly due to the proximity of a sync-exit of one block and
  the following sync-enter for another block.
  

Problem conclusion

• This defect will be fixed in:
  5.0.0 SR13
  6.0.0 SR10
  .
  The JIT compile has been modified to address this problem.
  .
  To obtain the fix:
  Install build 20100730 or later
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  IZ81066

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R600 PSN

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