PH67689: 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 to avoid a possible
  deadlock between CSOL and CWXN transactions when the region hits
  MAXSOCKETS.
  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 with PH64861 Applied.         *
  ****************************************************************
  * PROBLEM DESCRIPTION: All TCPIP functionality may stop        *
  *                      working when the region reaches         *
  *                      MAXSOCKETS.                             *
  ****************************************************************
  This is because code introduced by APAR PH64861 can result in
  CSOL attempting 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

• UO04038 UO03820 UO03821 UO04039
  
  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:

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

  PH69721 UO06688 UO06689 UO06690

Modules/Macros

• DFHAPDM  DFHASV   DFHCRC   DFHCRNP  DFHCRSP  DFHCSVC  DFHCZTRI
  DFHDBCR  DFHDBCT  DFHDMDM  DFHDMSVC DFHDSDM  DFHDSDS3 DFHDSMT
  DFHDSTCB DFHDT64M DFHDTDA  DFHDTDC  DFHDTLI  DFHDTLX  DFHDTRC
  DFHDTRI  DFHDTSS  DFHDTST  DFHDUDU  DFHDUSR  DFHDUSVC DFHEIQST
  DFHHPSVC DFHIEIE  DFHIEXM  DFHKEAR  DFHKEDD  DFHKEDS  DFHKEGD
  DFHKEIN  DFHKESTX DFHKETCB DFHKETIX DFHL2BS4 DFHL2CH4 DFHL2CHE
  DFHL2CHM DFHL2CHO DFHL2CHP DFHL2LB  DFHL2SR5 DFHL2WF  DFHLDDM
  DFHLDDMI DFHLDLB2 DFHLDLB3 DFHLDLD1 DFHLDLD2 DFHLDLD3 DFHLDSVC
  DFHLEPTD DFHLEPTI DFHMNDM  DFHMNSU  DFHMNSVC DFHMQIG  DFHMQSVC
  DFHNCSVC DFHPITH  DFHPSPSS DFHRXDM  DFHRXSVC DFHRXUW  DFHRZDM
  DFHRZIX  DFHRZLN  DFHRZNR2 DFHRZRG2 DFHRZRM  DFHRZRS1 DFHRZSO
  DFHRZSO1 DFHRZTA  DFHRZTCX DFHRZTR1 DFHRZTRI DFHRZXM  DFHS2PP
  DFHSIB1  DFHSIF1  DFHSIJ1  DFHSJNDI DFHSJPTI DFHSKC   DFHSMDM
  DFHSMPP  DFHSMSU  DFHSNTU  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  DFHSOSVC DFHSOTB  DFHSOTI
  DFHSOTRI DFHSOUE  DFHSOXM  DFHSPEJB DFHSPEJC DFHSPEJE DFHSPISB
  DFHSPISC DFHSPISE DFHSPSOB DFHSPSOC DFHSPSOE DFHSPWBB DFHSPWBC
  DFHSPWBE DFHSTP   DFHSTST  DFHTCDUF DFHWBA   DFHWBA1  DFHWBAP
  DFHWBAPF DFHWBBLI DFHWBCL  DFHWBDUF DFHWBSO  DFHWBSR  DFHWBSV
  DFHWBXM  DFHWBXN  DFHWSSN2 DFHWSSR  DFHWSTKV DFHWTI   DFHXCDMP
  DFHXCGUR DFHXCSVC DFHXSAD  DFHXSCT  DFHXSDM  DFHXSFL  DFHXSIS
  DFHXSKR  DFHXSLU  DFHXSPW  DFHXSRC  DFHZDSP  DFHZHPSR DFHZIS2
  DFHZXSTS DFJ@H360 EYU0VCTU EYU0XLIP
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UO06689

     UP26/02/07 P F602 ­

• R40M PSY UO06690

     UP26/02/07 P F602 ­

• R500 PSY UO06688

     UP26/02/05 P F602 ­

Fix is available

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