IT35039: EXCEPTION CAUGHT DURING QUERY OF SYSSCBLST TABLE MAY LEAVE MUTEXLOCKED WITH POTENTIAL FOR DEADLOCK

APAR status

• Closed as program error.

Error description

• The processing of a query for the pseudo table sysscblst in the
  sysmaster database may result in an exception which interrupts
  the query processing. The clean up of the query processing may
  leave a mutex named scbthd in a locked state which can later
  lead to a deadlock situation. The deadlock can be seen in the
  output of the "onstat -g wmx" command as in this example:
  
  Mutexes with waiters:
  mid      addr             name               holder   lkcnt
  waiter   waittime
  19       443a3838         session            19099537 0      20
  1729
  
  19099536 1729
  718290922 21044fca0        scbthd             19099536 0
  19094197 1729
  
  19099537 1729
  
  The thread with id 19099537 is the holder of the session mutex
  and is waiting for access to the scbthd mutex. The thread
  holding that mutex, with id 19099536, is waiting for the session
  mutex and the result is deadlock. A typical stack for the thread
  holding the session mutex may be:
  
  yield_processor_mvp
  mt_lock_wait
  mt_lock_helper
  mt_prscblst
  pstread
  pst_rsread
  rsread
  fmread
  readseq_single
  gettupl
  scan_next
  hjoin_next
  hjoin_next
  sort_open
  prepselect
  open_cursor
  sql_open
  sq_open
  sqmain
  
  An example stack for the thread holding the scbthd mutex may be:
  
  yield_processor_mvp
  mt_lock_wait
  mt_lock_helper
  destroy_session
  sq_exit
  sqmain
  
  Other stacks for this thread may be possible.
  
  Queries using the sysmaster view syssessions are also
  susceptible.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * Users of Informix Server prior to 12.10.xC15 and 14.10.xC6.  *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Upgrade to Informix Server 12.10.xC15 (when available) or    *
  * 14.10.xC6 (when available).                                  *
  ****************************************************************
  

Problem conclusion

• Fixed in Informix Server 12.10.xC15 and 14.10.xC6.
  

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

  INFORMIX SERVER

• Fixed component ID

  5725A3900

Applicable component levels