PM24571: DVIPA CREATE/DELETE HELD MUCB LOCK RESULTING IN LOCK CONTENTION AND UNEXPECTED MULTIPLE ABENDS IN TCPIP AND VARIOUS APPLICATIONS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• When a UDP socket is being closed at the same time as the
  SIOCBEGINPROFILE processing for a DVIPA add/delete, lock
  contention can occur. Because a DVIPA at bind() time was
  created by the UDP socket, it gets deleted at close time
  via a call from EZBUDSTR while the MUCB lock is held. This
  lock contention can result in multiple abends for various
  applications and can impact availability and recoverability.
  For example, OMPROUTE might not be responsive resulting in
  TCPIP abend S04C5 and not recover. In this case, restarting
  OMPROUTE might temporarily relieve the problem.
  
  Example ABENDS resulting from lock contention
  ----------------------------------------------
  TCPIP    S04C5-77620405 IN EZBXFPUDX(HIP61A0 08.091)+0003BE
  VTAM     S013E
  NETVIEW  S0EC4-101
  
  Diagnosis
  ---------
  TCPIPCS LOCK report will show indication of a MUCB lock being
  held and in contention.
  
    7EF0FC40 19AE4000 Held Excl            UCB
    7F221388 19B26000 Held Excl EnqH       MUCB
    ...
             19B02000 Wait Excl
    7E9CD9F8 19AF0000 Held Excl EnqH       TCB
             19AD5000 Wait Excl
    1CAC2348 19B02000 Held Excl EnqH       IELOCK
    ...
             19B26000 Wait Excl
    1AA37318 19B26000 Held Excl EnqH       XCF
             19AB1000 Wait Excl
    ...
  The DUCB holding the MUCB lock is 19B26000. TCPIPCS DUAF
  report will show the following calling sequence:
  
    1000002F 1AA351A8 19B26000 19B261A0 00F4F100 00BC CFZCIM
    00000000 Iu Su
    RSA  19B26668  Prev 238A73E0  Next 19B26800  Mod EZBPFCLS
    RSA  19B26808  Prev 19B26668  Next 19B26B68  Mod EZBPFCLO
    RSA  19B26B70  Prev 19B26808  Next 19B27150  Mod EZBUDSTR <--
    RSA  19B27158  Prev 19B26B70  Next 19B27938  Mod EZBXFUDV
    RSA  19B27940  Prev 19B27158  Next 20633038  Mod EZBXFDYN
   ...
  

Local fix

• Do a TCPIP recycle or restart of the affected application to
  release the lock.
  
  KEYWORDS:
  DVIPA MUCB LOCK UDP SIOCBEGINPROFILE BEGINPROFILE EZBUDSTR BIND
  VTAM NETVIEW OMPROUTE SYSPLEXMONITOR RECOVERY
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communications Server   *
  *                 for z/OS Version 1 Release(s) 10, 11 and 12  *
  *                 IP                                           *
  ****************************************************************
  * PROBLEM DESCRIPTION: TCPIP hangs during UDP close socket     *
  *                      processing.                             *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  A UDP multicast registered socket bound to a dynamic VIPA
  causes the DVIPA to be deleted when the socket is closed.
  The close processing holds the MUCB lock and waits to obtain
  the IELOCK.
  In V1R10 and V1R11 simultaneous OBEYFILE processing
  holds the IELOCK and waits to obtain the MUCB lock.
  Close and OBEYFILE processing come to a deadlock. TCPIP hangs.
  In V1R12 the close processing holds the MUCB lock and continues
  by scheduling and waiting for an asynchronous process. The
  asynchronous process also reqeuests the MUCB lock.
  The close process holds the MUCB lock while the asynhronous
  process waits for the lock. Both processes are deadlocked.
  TCPIP hangs.
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

• The socket CLOSE process that makes the call to delete the
  DVIPA in EZBUDSTR has been changed to release the MUCB lock
  before making the call to delete the DVIPA.
  
  * Cross Reference between External and Internal Names
  

Temporary fix

• *********
  * HIPER *
  *********
  

Comments

APAR Information

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

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

  UK62116 UK62117 UK62118

Modules/Macros

• EZBUDSTR
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R1A0 PSY UK62116

     UP10/12/18 P F012 Ž

• R1B0 PSY UK62117

     UP10/12/18 P F012 Ž

• R1C0 PSY UK62118

     UP10/12/18 P F012 Ž

Fix is available

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