PH69721: CSOL CAUSES DEADLOCK TRYING TO GET EXCLUSIVE SOLOCK WHEN IT ALREADY HAS SHARED SOLOCK 25/10/20 PTF PECHANGE

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• APAR PH64861 introduced some code changes into CICS TS 6.1 and
  CICS TS 6.3 to avoid a possible deadlock between CSOL and CWXN
  transactions when the region hits MAXSOCKETS. This code is in
  base at CICS TS 6.3.
  However, the new code introduced a path where CSOL
  can obtain a shared lock on the SOLOCK before trying to obtain
  an exclusive lock on the SOLOCK. CSOL is then placed on the wait
  queue for the SOLOCK and any other tasks wanting this lock also
  back up behind it.
  
  
  CSOL begins processing a new connection and obtains the shared
  SOLOCK. It starts to add a new socket but finds that we are
  already at MAXSOCKETS. So, it decides to close an unowned
  socket; however, it needs to hold the SOLOCK exclusively to do
  this. CSOL does not realize it already owns a shared lock on the
  SOLOCK, so when it requests an exclusive lock, it enters a
  self-imposed deadlock.
  
  KIXREVACC
  

Local fix

• The CICS region needs to be recycled.
  
  The issue is at risk of occurring when the region hits its
  MAXSOCKETS value. It may be possible to avoid this issue by
  increasing the MAXSOCKETS value for the region as well as
  setting a SOCKETCLOSE attribute on TCPIPSERVICE and URIMAP
  definitions.
  
  
  The SOCKETCLOSE attribute determines how long CICS will keep
  an unowned socket open. This is measured from the time of the
  last I/O and that timer will be reset when more I/O occurs.
  Setting an appropriate SOCKETCLOSE value will allow CICS to
  close unused connections, thus delaying the possibility of
  hitting the MAXSOCKETS value.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS Users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: All TCPIP functionality may stop        *
  *                      working when the region reaches         *
  *                      MAXSOCKETS.                             *
  ****************************************************************
  CSOL can attempt to obtain the SOLOCK EXCLUSIVE when it
  currently holds the SOLOCK shared. This results in CSOL
  becoming deadlocked on itself.
  
  This situation arises if the region is at MAXSOCKETS when CSOL
  is processing a new connection and it is found that there is an
  eligible socket to be reused. The issue presents when an attempt
  is made to close this socket for reuse by the incoming request.
  

Problem conclusion

• CICS has been changed to avoid CSOL attempting to obtain the
  SOLOCK EXCLUSIVE in this code path.
  

Temporary fix

Comments

APAR Information

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

  PH67689

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

  UO06691

Modules/Macros

• DFHCZTRI DFHIEIE  DFHIEXM  DFHPITH  DFHRZDM  DFHRZIX  DFHRZLN
  DFHRZNR2 DFHRZRG2 DFHRZRM  DFHRZRS1 DFHRZSO  DFHRZSO1 DFHRZTA
  DFHRZTCX DFHRZTR1 DFHRZTRI DFHRZXM  DFHSOAD  DFHSOCK  DFHSOCKT
  DFHSODM  DFHSODS  DFHSODUF DFHSOES  DFHSOHN  DFHSOIS  DFHSOL
  DFHSOLI  DFHSOLS  DFHSOLX  DFHSOLX6 DFHSOM01 DFHSOM02 DFHSOM03
  DFHSONT  DFHSOPL  DFHSORD  DFHSORL  DFHSORM  DFHSOS00 DFHSOS01
  DFHSOS02 DFHSOS03 DFHSOS04 DFHSOS05 DFHSOS06 DFHSOS07 DFHSOS08
  DFHSOS09 DFHSOS10 DFHSOS11 DFHSOS12 DFHSOS13 DFHSOS14 DFHSOS15
  DFHSOS16 DFHSOS17 DFHSOS18 DFHSOS19 DFHSOS20 DFHSOS21 DFHSOS22
  DFHSOS23 DFHSOSE  DFHSOSES DFHSOSM  DFHSOST  DFHSOTB  DFHSOTI
  DFHSOTRI DFHSOUE  DFHSOXM  DFHWBA   DFHWBA1  DFHWBAP  DFHWBAPF
  DFHWBBLI DFHWBCL  DFHWBSO  DFHWBSR  DFHWBSV  DFHWBXM  DFHWBXN
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R600 PSY UO06691

     UP26/02/05 P F602 ¢

Fix is available

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