IC70228: ONPLOAD SEGV DUE TO STACK OVERFLOW SOON AFTER FORKING A CONVERT THREAD AND ADDING A NEW ONPLOAD SHARED MEMORY SEGMENT

APAR status

• Closed as fixed if next.

Error description

• In certain circumstances, an onpload frontend thread may
  overflow its stack.  This problem is more likely to be seen on
  HP Itanium.  You need a new onpload shared memory segment to be
  added at the same time as the fork of the new convert thread for
  the problem to occur.
  
  By onpload shared memory segments, I mean the onpload private
  shared memory segments that start with 0x49 key --
  
  Example:
  
  $ ipcs -m | grep 0x49
  
  m    6094866 0x49010000 --rw-rw----  informix  informix  <---
  onpload R segment
  m    5668883 0x49010001 --rw-rw----  informix  informix  <---
  onpload initial V segment
  m    5931028 0x49010002 --rw-rw----  informix  informix  <---
  onpload new V segment added after startup
  
  Note:  The onpload stack size and the sizes of the onpload
  segments are not configurable.
  
  The problem occurs rarely and randomly during onpload job start
  -- when the problem segv does occur, if you have tracing turned
  on, you will see a line like this in the trace file:
  
  02:29:28 - FORKED(worker, 12): convert 25
  ...
  02:29:28 - plsig_segv(convert, 25): signal received
  
  
  If you do not have tracing turned on, you may see a plsig_segv()
  message in stderr/stdout, but it probably will not say where it
  came from.
  
  The same job, when re-run may not run into the problem again.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Informix 11.50, HP-UX Itanium 11.23                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * onpload may crash or hang shortly after a new shared memory  *
  * segment is added.                                            *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to Informix 11.50.xC8 or higher.                     *
  ****************************************************************
  

Problem conclusion

Temporary fix

Comments

• For download information, go to:
  http://www.ibm.com/support/fixcentral
  

APAR Information

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

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

Fix information

Applicable component levels

• RB15 PSN

     UP

• RB15 PSY

     UP