LKWRD

Prolog  

Control Block Contents  
   LKWRD DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  

LKWRD Prolog

 Name       : HCPLKWRD
 Description: Defer-lock "lockword"
 DSECT      : LKWRD
 Function   : The lockword the means of serializing
              deferrable requests for access to a group of
              data by different tasks.
 Located by : Various lockwords to protect specific classes
              of data exist inside other control blocks
              and data areas (VMDBK, SYSCM, HCPRCC, etc.)
 Created by : none (lockwords are static, or are "created"
              within other dynamically created blocks
              e.g., the VMDBK).
 Deleted by : none (lockwords are static, or are "deleted"
              within other dynamically deleted blocks.

LKWRD Control Block Content

LKWRD DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      LKWRD          Defer-lock "lockword"
0000    0 Dbl-Word     8 LKWCSWAP (0)   Doubleword updated by Compare and
                                        Swap
0000    0 Signed       4 LKWSTATE       Current lock state. See module
                                        prologue of HCPLCK for details.
0004    4 Address      4 LKWQUEUE       Pointer to chain of deferred
                                        CPEBK's
0008    8 Dbl-Word     8 LKWQQTOD       TOD saved at last
                                        enqueue/dequeue. (Only stamped if
                                        there's a queue.)
0010   16 Bitstring    1 LKWFLG1        Miscellaneous lock flags
          1... ....      LKWLTLK        X'80' Non-critical attribute,
                                        critical process count does not
                                        get decremented or incremented
                                        for this lock.
0011   17 Bitstring    3 LKWDQLEN       Current length of defer queue.
0014   20 Signed       4 LKWDYTOD       TOD saved at start of last
                                        "delay" period. It's the time the
                                        lock was last granted (if there
                                        was a queue at that time) or the
                                        time at which the queue size last
                                        changed from 0 to 1. Units are
                                        TOD with bits 32-63 discarded.
          00000003       LKWRDSIZ       (*-LKWRD)/8 Size of lockword in
                                        doublewords
     The following re-definition of LKWSTATE allows addressability to the
     last byte to check for a lockword held exclusive. This is NOT intended
     for general use; it is used by HCPWAI (Active Wait) for a specific
     purpose and may NOT be accurate for all locks. See the prologue of
     HCPLCK for a complete description of LKWSTATE.
0000    0 Bitstring    1 * (3)          (don't care about 1st 3 bytes)
0003    3 Bitstring    1 LKWSTAT4       4th byte of LKWSTATE
          .... ...1      LKWEXCL        X'01' Lock held EXCLUSIVE

LKWRD Storage Layout

          
*** LKWRD - Defer-lock "lockword"
*
*     +---------------------------+---------------------------+
*   0 |         LKWSTATE          |         LKWQUEUE          |
*     +---------------------------+---------------------------+
*   8 |                       LKWQQTOD                        |
*     +------+--------------------+---------------------------+
*  10 |:FLG1 |     LKWDQLEN       |         LKWDYTOD          |
*     +------+--------------------+---------------------------+
*  18
*
*** LKWRD - Defer-lock "lockword"
          
*** Overlay for LKWSTATE in LKWRD
*
*     +--------------------+------+
*   0 |////////////////////|:STAT4| 4
*     +--------------------+------+
*
*** Overlay for LKWSTATE in LKWRD

LKWRD Cross Reference

Symbol         Dspl Value
-------------- ---- -----
LKWCSWAP       0000
LKWDQLEN       0011
LKWDYTOD       0014
LKWEXCL        0003 01
LKWFLG1        0010
LKWLTLK        0010 80
LKWQQTOD       0008
LKWQUEUE       0004
LKWRDSIZ       0014 00000003
LKWSTATE       0000
LKWSTAT4       0003