IV19697: APPLICATION HANG WITH HIGH CPU UTILIZATION

APAR status

• Closed as program error.

Error description

• Error Message: The Java application stops making progress while
  still using CPU resources (livelock)
  .
  Stack Trace: The native stack trace will most likely contain
  functions related to allocation and freeing of optimization
  plans used by the JIT
  .
  

Local fix

Problem summary

• This rare problem needs all of the following conditions to
  occur:
  (1) Two compilation requests for the same method occur in
  parallel.
  (2) GC has requested all threads to stop because it wants to
  proceed exclusively
  (3) The application uses Compiler.disable() interface to disable
  JIT operation
  (4) The requested compilation is a synchronous one which is a
  rare event in itself
  These conditions can lead to a situation where one compilation
  request has just started, but stopped because of the GC request.
  The GC is blocked because of another Java thread not yielding.
  The other Java thread continuously tries to compile the same
  method, but cannot because JIT is disabled (due to
  Compiler.disable call) and at the same time cannot abort the
  compilation because another attempt is already in progress
  

Problem conclusion

• This defect will be fixed in:
  6.0.1 SR2
  7.0.0 SR1
  .
  The situation described in the "Problem Summary" has been
  addressed by forcing the second Java thread to yield to GC and
  wait for the compilation result (despite the Compiler.disable
  directive). This allows GC to continue which then unblocks the
  compilation thread which unblocks the two Java threads waiting
  for the compilation result
  

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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