PJ40922: CTL-571/CTL-10'S MAY OCCUR WHEN APPLYING PJ40471

APAR status

• Closed as program error.

Error description

• See Problem Summary.
  

Local fix

• na
  

Problem summary

• APAR NUMBER:  PJ40922
  PRODUCT:  z/TPF
  FUNCTIONAL AREA:  ENTER/BACK PROCESSING
  SHIPPED IN PUT:  10
  
  ABSTRACT:
  CTL-571 and CTL-10 may occur when applying PJ40471.
  
  PACKAGE CONTENTS:
  Source Segments:
  (C) base/cp/cpsm.cpy
  (C) base/cp/cceh.cpy
  
  Object Only Binaries:
  None.
  
  Configuration Independent Binaries:
  None.
  
  Support Files:
  None.
  
  OTHER BINARIES TO BUILD: YES
  (C) <sys>/load/CPS0.so
  (C) <sys>/obj/cccpse.o
  (C) <sys>/obj/ccenbk.o
  
  COMMENTS:
  PJ40471 changed CCENBK routine CCEHOLD to replace the MONTC
  call with a Set PSW Key from Address (SPKA) instruction. One
  reason that the MONTC was executed is to change the protect
  key. The SPKA can also change the protect key and the overhead
  is much less. However, when MONTC is executed in the CP, I/O
  interrupts are also disabled.
  
  Because PJ40471 removed the MONTC, the CCEHOLD routine is now
  enabled for I/O interrupts. If an I/O interrupt is taken in the
  CCEHOLD routine it is possible that a deadly embrace between
  core locks may occur. To create this situation, a multiple
  entry point CSO program must be loaded and activated using the
  online loader (OLD). The activation of the multiple entry point
  CSO will cause routine CCEHOLD to be executed on entry to the
  program in order to determine which version to use. When ECBs
  on separate I-streams are entering the activated program at the
  same time and an I/O interrupt is taken in CCEHOLD and this I/O
  interrupt attempts to obtain a lock, it is possible that a
  deadly embrace can happen.
  
  As an example assume that CTAL was online loaded and activated.
  Next, I-stream 2 obtains the socket block table lock (CINFC
  CMMCTK2 field ck2sokb) in an E-type program. While holding this
  lock the E-type program calls a C function in CTAL. The linkage
  to CTAL will go to routine CCEHOLD and a LOCKC on the base PAT
  slot for CTAL is executed. While this is happening, I-stream 3
  is also entering a C function in CTAL and it also goes to
  routine CCEHOLD. In this example, I-stream 3 obtains the PAT
  lock for CTAL first. After I-stream 3 obtains the lock and
  while it is still in CCEHOLD, an I/O interrupt is taken. The
  I/O interrupt is for an OSA SDA. As a result the first level
  interrupt routine in CIO attempts to get the socket block table
  lock. The result is a deadlock between core locks. I-stream 2
  has the socket block table lock and wants the PAT lock for
  CTAL. I-stream 3 has the PAT lock for CTAL and wants the socket
  block table lock. Eventually, a CTL-571 will happen. In
  addition, in this example if an E-type program on another
  I-stream attempts to get the socket block table lock, it will
  take a CTL-10.
  

Problem conclusion

• SOLUTION:
  The solution is to recognize that an I/O interrupt is being
  processing and that the I/O interrupt is attempting to get a
  lock and that the I/O interrupt happened in the CCEHOLD
  routine. If the PAT entry that is being used in CCEHOLD is
  locked by the I-stream that took the I/O interrupt, I/O
  interrupt processing will unlock the PAT entry and set the I/O
  interrupt return address to return to the LOCKC in CCEHOLD.
  
  The actual implementation is in the LOCKC monitor call routine
  in CCCPSE cpsm.cpy. When the first LOCKC monitor call for a
  specific lock request is executed, processing goes to label
  RESETCOUNT in cpsm.cpy. At this point logic is inserted to
  recognize the special I/O interrupt handling. The following
  checks are performed:
  (a) If processing is in I/O interrupt processing, continue.
  Otherwise, skip the special CCEHOLD logic.
  (b) If the I/O interrupt happened in CCEHOLD, continue. This
  check is done based on newly added labels in cceh.cpy. If the
  I/O interrupt is not in CCEHOLD, skip the special CCEHOLD logic.
  (c) If the monitor call interrupt happened in CIO, continue.
  Otherwise, skip the special CCEHOLD logic.
  (d) Obtain the ECB application stack address from the I/O
  interrupt saved registers. In CCEHOLD, R15 contains the stack
  frame address. If the stack address is valid, continue.
  Otherwise, skip the special CCEHOLD logic.
  (e) Obtain the address of the PAT from the ECB application
  stack at label ICST_BR8. CCEHOLD has been updated to save the
  PAT address at ICST_BR8. If the PAT address is valid, continue.
  Otherwise, skip the special CCEHOLD logic.
  (f) If the base PAT entry is locked by the I-stream that is
  processing the I/O interrupt, continue. Otherwise, skip the
  special CCEHOLD logic.
  (g) If all the proceeding checks have been passed, the special
  CCEHOLD logic is executed.
  (h) The base PAT entry is unlocked.
  (i) The I/O interrupt saved value for R7 is changed to contain
  the address of the base PAT entry for the program being
  entered. CCEHOLD may change R7. The return location expects
  that R7 will point to the base PAT entry.
  (j) The I/O interrupt return address is changed to go to label
  CCEH_START_SPECIAL_HANDLING in CCENBK cceh.cpy.
  (j) If the key on entry to CCEHOLD was not Key 0, the I/O
  interrupt PSW key is changed to be key E.
  Finally, processing continues in LOCKC monitor call routine
  RESETCOUNT.
  
  COREQS: NO
  None.
  
  MIGRATION CONSIDERATIONS: NO
  None.
  
  BUILD COMMANDS AND INSTRUCTIONS: YES
  #maketpf commands for linux
  maketpf -f CPS0 cccpse.o ccenbk.o
  maketpf CPS0 link
  
  UPDATED INFORMATION UNITS: NO
  None.
  
  See your IBM representative if you need additional information.
  
  DOWNLOAD INSTRUCTIONS:
  http://www.ibm.com/software/htp/tpf/maint/maintztpf.html
  
  APAR URL:
  http://www.ibm.com/software/htp/tpf/ztpfmaint/put10/PJ40922.htm
  

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:

Fix information

• Fixed component name

  Z/TPF

• Fixed component ID

  5748T1501

Applicable component levels

• R110 PSY

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