NAME       : HCPALCBK
 DESCRIPTION: Access-List Control Block
 DSECT      : ALCBK
 FUNCTION   : This DSECT maps the control block used to manage an
              ESA/370 access list.
 LOCATED BY : ALEALCBK in the second access-list entry of an access
              list built by CP (the one with ALEN=1).
 CREATED BY : HCPALMCR when an access list is created.
 DELETED BY : HCPALMDS when an access list is destroyed.
 RELOCATION CONSIDERATIONS : None
 NOTES      : Serialization of the access-list depends on whether the
              list is the CP-use access list, or a guest-use access
              list:
              For the CP-use access list:
              - An ALE is validated using CDSG.
              - If no ALE is available, the ATTACH task is
              suspended to await an available entry.  The
              queue of deferred tasks is anchored in ALCDEFRQ.
              - The deferred task at the head of the queue is
              driven on a subsequent DETACH.
              - ALCDEFRQ and ALCFREE (count of available ALEs)
              are in the same doubleword, and are modified
              using CSG.  This technique closes a window where
              an ATTACH task is in the process of deferring,
              while a DETACH is in progress.
              - Since multiple tasks can be deferred, the
              ALCLOCK is obtained when manipulating the
              ALCDEFRQ queue.
              For a guest-use access list:
              - The ALCLOCK controls all changes to the ALCBK.

 ALCBK DSECT
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Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      ALCBK          Access-List Control Block
                                  block.
0000    0 Address      4 ALCALD         Address of access-list
                                        designation.
0004    4 Address      4 ALCAL          Address of access list
0008    8 Address      4 ALCOWNER       Address of VMDBK which owns the
                                        access list.
000C   12 Signed       4 *              Reserved for IBM use
0010   16 Address      4 ALCSPIBK       Anchor for chain of SPIBKs
                                        defining what address spaces may
                                        be attached to this access list.
                                        This is serialized by the
                                        space-permission-manager lock
                                        (RSASPMLK in HCPRSMCM).
0014   20 Signed       4 *              Reserved for IBM use.
0018   24 Dbl-Word     8 ALCLOCK (3)    Lockword for access-list-control
                                        lock.
0030   48 Signed       4 ALCALSIZ       Size of access list, in bytes.
0034   52 Signed       4 ALCMAXSZ       Largest permitted size of access
                                        list, in bytes.
0038   56 Signed       8 ALCCSDWD (0)   Queue hdr and available count.
                                        Serialized with CSG for the
                                        CP-use access list. See ALCBK
                                        prolog for details.
0038   56 Address      4 ALCDEFRQ       Anchor for queue of tasks adding
                                        entries to the CP-use AL which
                                        have been deferred because the
                                        CP-use access list is full.
003C   60 Signed       4 ALCFREE        Number of ALEs in the invalid
                                        state (not including ALENs 0 and
                                        1). This is the number of ALEs
                                        available for allocation.
          00000040       ALCLEN         *-ALCBK Length in bytes of ALCBK.
          00000008       ALCSIZE        (ALCLEN+7)/8 Size in doublewords
                                        of an ALCBK

          
*** ALCBK - Access-List Control Block
*
*     +---------------------------+---------------------------+
*   0 |          ALCALD           |          ALCAL            |
*     +---------------------------+---------------------------+
*   8 |         ALCOWNER          |///////////////////////////|
*     +---------------------------+---------------------------+
*  10 |         ALCSPIBK          |///////////////////////////|
*     +---------------------------+---------------------------+
*  18 |                                                       |
*     =                       ALCLOCK                         =
*     |                                                       |
*     +---------------------------+---------------------------+
*  30 |         ALCALSIZ          |         ALCMAXSZ          |
*     +---------------------------+---------------------------+
*  38 |         ALCDEFRQ          |         ALCFREE           |
*     +---------------------------+---------------------------+
*  40
*
*** ALCBK - Access-List Control Block

 
Symbol         Dspl Value
-------------- ---- -----
ALCAL          0004
ALCALD         0000
ALCALSIZ       0030
ALCCSDWD       0038
ALCDEFRQ       0038
ALCFREE        003C
ALCLEN         003C 00000040
ALCLOCK        0018
ALCMAXSZ       0034
ALCOWNER       0008
ALCSIZE        003C 00000008
ALCSPIBK       0010