PH64861: DEADLOCK BETWEEN CSOL AND CWXN TASKS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Following a surge in incoming work the customer found that
  CWXN transactions hung. From a dump provided it could be
  seen that this was due to a deadlock between CSOL and CWXN
  tasks. In addition MAXSOCKETS had been hit.
  
  CWXN tasks were using all of the S8 TCBs (MAXSSLTCBS had been
  reached). These tasks were all waiting to acquire the SOLOCK
  and this was held by CSOL. CSOL needed to switch to an
  S8 TCB in order to close a socket, hence the deadlock.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICS Users.                              *
  ****************************************************************
  * PROBLEM DESCRIPTION: A surge in incoming web requests in a   *
  *                      region can cause a deadlock between     *
  *                      CSOL and CWXN tasks as a result of      *
  *                      contention for the SOLOCK.              *
  ****************************************************************
  A surge of work results in the region hitting the MAXSOCKETS
  limit. When CSOL processes an new incoming connection, the
  SOLOCK is obtained exclusively and maxsockets processing finds a
  socket that be reclaimed for this new connection. The socket to
  be reclaimed was used for SSL work and so an S8 TCB is needed in
  order to close this socket. However, all the S8 TCBs in the
  region are in use by CWXN tasks that are processing HTTP
  requests.
  
  These are all waiting for the SOLOCK that CSOL currently
  holds exclusively. CSOL can not continue without an S8 TCB,
  the CWXN tasks holding the S8 TCBS can not continue without
  CSOL freeing the SOLOCK.
  

Problem conclusion

• DFHSOLS has been updated so that CSOL obtains the SOLOCK
  exclusively later in the processing of accepting a new
  connection.
  

Temporary fix

Comments

• ×**** PE25/10/01 FIX IN ERROR. SEE APAR PH64861  FOR DESCRIPTION
  ×**** PE25/10/01 FIX IN ERROR. SEE APAR PH64861  FOR DESCRIPTION
  ×**** PE25/10/01 FIX IN ERROR. SEE APAR PH64861  FOR DESCRIPTION
  ×**** PE25/10/01 FIX IN ERROR. SEE APAR PH64861  FOR DESCRIPTION
  ×**** PE25/10/01 FIX IN ERROR. SEE APAR PH64861  FOR DESCRIPTION
  ×**** PE25/10/01 FIX IN ERROR. SEE APAR PH64861  FOR DESCRIPTION
  

APAR Information

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

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

  UO03820 UO03821

Modules/Macros

• DFHSOLS
  

Fix information

• Fixed component name

  CICS TS Z/OS V6

• Fixed component ID

  5655YA100

Applicable component levels

• R400 PSY UO03821

     UP25/06/27 P F506

• R500 PSY UO03820

     UP25/06/27 P F506

Fix is available

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