IV26972: MULTIPLE THREADS STUCK IN PARKED STATE

APAR status

• Closed as program error.

Error description

• Error Message: The JVM hangs while multiple threads are parked
  on the same lock (e.g. a
  java/util/concurrent/locks/ReentrantLock$NonfairSync object).
  The thread that is supposed to wake all the parked threads is
  also incorrectly stuck in the parked state so all the threads
  remain parked and never wake up.
  .
  Stack Trace: sun/misc/Unsafe.park
  java/util/concurrent/locks/LockSupport.park
  java/util/concurrent/locks/AbstractQueuedSynchronizer.parkAndChe
  ckInterrupt
  java/util/concurrent/locks/AbstractQueuedSynchronizer.acquireQue
  ued
  java/util/concurrent/locks/AbstractQueuedSynchronizer.acquire
  java/util/concurrent/locks/ReentrantLock$NonfairSync.lock
  java/util/concurrent/locks/ReentrantLock.lock
  java/util/concurrent/ArrayBlockingQueue.offer
  .
  

Local fix

Problem summary

• The problem occurs when the Java code depends on volatile
  semantics to ensure that the volatile field updates are seen in
  different threads. The problem is caused by incorrect volatile
  field handling in JIT-compiled code. A memory fence for a
  volatile field is missing after a write operation due to
  incorrect JIT code generation. This issue affects z/OS and
  z/Linux, running on z9 or older hardware.
  

Problem conclusion

• This defect will be fixed in:
  5.0 SR15
  6.0 SR12
  
  6.0.1 SR3
  7.0.0 SR2
  .
  The JIT compiler has been updated to generate the memory fence
  if the field is found to be a volatile.
  

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:

  IV29907

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R260 PSY

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