IT35284: READAHEAD THREAD MAY NOT RECEIVE WAKEUP CALL RESULTING IN HANG OF OTHER THREADS

APAR status

• Closed as program error.

Error description

• A ReadAhead thread will enter a wait state when it finds no
  requests to be serviced and will then be woken up by another
  thread when such a request is made. A timing window exists where
  the wakeup request may not be serviced as intended and the
  readahead request is not serviced immediately. If there are no
  further readahead requests made then the problem request will
  remain in a pending state which may cause its requesting thread
  to hang at a later point in time.
  
  In one scenario the thread named "bld_logrecs" may hang at the
  end of logical recovery with a stack of the form:
  
  (oninit)yield_processor_mvp
  (oninit)mt_yield
  (oninit)ra_terminate_req
  (oninit)ra_free_req
  (oninit)bld_logrecs
  (oninit)startup
  
  This will cause the Informix server to remain in the Fast
  Recovery state and a restart may be required. This issue may be
  observed in versions including the fix for IT32067, first
  released in 14.10.xC5.
  

Local fix

• If stuck in the Fast recovery state then issuing the command
  "onbar -b -l" should help to resolve the problem. If not then
  the Informix server should be restarted whereupon it may
  successfully complete Fast Recovery. Due to the nature of the
  timing window the server may become stuck again in which case
  temporarily reducing the number of CPU VPs to 1 followed by a
  further restart should allow it to complete Fast Recovery.
  

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