PN88110: ABEND4C5 8C7 IN EZAT2SUT.

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• ABEND4C5 8C7 in EZAT2SUT.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of TCP/IP for MVS                  *
  ****************************************************************
  * PROBLEM DESCRIPTION:  ABEND4C5 8C7 in EZAT2SUT.              *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The problem happens only under heavy stress.
  
  EZAS2GET is called when there are no more cells on the free
  queue for that cell pool during a GetCell operation.  EZAS2GET
  locks the Cpcb and then copies the Cpcb to local storage, where
  it is modified during the get operation.  Once the operation is
  complete, the local Cpcb is copied back to the original Cpcb.
  However, this is where the problem can occur.  During this
  time, other tasks will be doing GetCell and FreeCell operations
  against that Cpcb which will cause the free queue pointer in
  the Cpcb to be modified.  Then when the local Cpcb is copied
  back to the original Cpcb, the free queue pointer is
  back-leveled back to the point where the Cpcb was copied.  Thus,
  the next time an application attempts to do a GetCell or
  FreeCell operation, it will be using compare/swap with the
  back-level free queue pointer rather than the previously
  updated free queue pointer, thus working with cells that may
  have already been obtained or freed.
  
  For example:  If a cell was obtained prior to the lock, then
  the free queue pointer would have been updated past that cell.
  Then the Cpcb is copied back to the original, with the free
  queue pointer pointing to the cell that was just obtained.  The
  next GetCell operation will cause a 4c5/8c7 since the cell was
  just allocated.
  

Problem conclusion

• Only selected fields are now copied to the original Cpcb during
  a EZAS2GET operation so that the Cpcb free queue counter as
  well as other Cpcb fields that are independent of the lock are
  not corrupted.
  
  Additional Keywords: MV12235 DV12235 ABEND4C5
  

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:

  UN94404

Modules/Macros

• EZAS2GET
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R320 PSY UN94404

     UP96/09/04 P F608

Fix is available

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