IV53361: HIGH CPU WITH THREADPOOLEXECUTOR.GETTASK() IN SHUTDOWN MODE

APAR status

• Closed as program error.

Error description

• Error Message: 100% CPU is observed when trying to execute tasks
  scheduled for future from
  java.uti.concurrent.ScheduledThreadPoolExecutor in SHUTDOWN
  mode.
  .
  Stack Trace: A stack trace generated during high CPU shows the
  following
  at
  java/util/concurrent/ThreadPoolExecutor.getTask(ThreadPoolExecut
  or.java:969(Compiled Code))
  at
  java/util/concurrent/ThreadPoolExecutor$Worker.run(ThreadPoolExe
  cutor.java:918)
  at java/lang/Thread.run(Thread.java:736)
  .
  

Local fix

• Ensure no task exists which is scheduled  for future while
  calling shutdown() method on a
  java.util.concurrent.ScheduledThreadPoolExecutor.
  

Problem summary

• java.util.concurrent.ThreadPoolExecutor.getTask()used a poll()
  method of DelayQueue to get the task during Shutdown. The poll()
   return null when a future scheduled task is not expired. Hence,
  it can result in a tight loop as the getTask()will return only
  when the task is empty or a task is ready.
  

Problem conclusion

• This defect will be fixed in:
  6.0.0 SR16
  6.0.1 SR8
  .
  The JDK has been updated to make the
  java.util.concurrent.ThreadPoolExecutor.getTask() to wait for
  the future scheduled task to get expired during Shutdown instead
  of spinning till the future scheduled task is expired.
  

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

  JAVA CLASS LIBS

• Fixed component ID

  620700130

Applicable component levels