Type ASSEMBLE
Source Lines : 620
Fixes Applied : 4
Most Recent Version : Tuesday, December 12, 1978
Last Fix ID : [R14218DS]
Module
DMSSMN
Function
THE DMSSMN ROUTINE PROCESSES OS FREEMAIN AND GETMAIN
MACROS, AND CMS CALLS TO DMSSMNSB (STRINIT).
Attributes
NUCLEUS RESIDENT, RE-ENTRANT
Operation
IF AN OS GETMAIN OR FREEMAIN IS ISSUED WITH AN R
OPERAND, CONTROL IS PASSED VIA AN SVC10 TO THE SVC10
ENTRY POINT IN DMSSMN. DMSSMN ROUNDS THE AMOUNT OF
STORAGE SPECIFIED UP TO A DOUBLEWORD AND DETERMINES IF
A GETMAIN OR FREEMAIN WAS ISSUED. IF A GETMAIN WAS
ISSUED, THE GETBLK ROUTINE IN DMSSMN IS CALLED TO GET A
FREE STORAGE BLOCK. CONTROL IS THEN RETURNED TO THE
USER WITH THE ADDRESS OF THE FREE STORAGE IN REGISTER
ONE. IF A FREEMAIN WAS ISSUED, THE FREEBLK ROUTINE IN
DMSSMN IS CALLED TO RELEASE A BLOCK OF STORAGE AND
CONTROL IS RETURNED TO THE USER.
IF AN OS GETMAIN IS ISSUED WITHOUT AN R OPERAND,
CONTROL IS PASSED VIA AN SVC4 TO THE SVC4 ENTRY
POINT IN DMSSMN. IF THE GETMAIN WAS NOT VARIABLE,
DMSSMN ROUNDS UP THE AMOUNT OF STORAGE SPECIFIED AND
CALLS THE GETBLK ROUTINE IN DMSSMN TO GET A FREE
STORAGE BLOCK. CONTROL IS THEN RETURNED TO THE USER
WITH THE ADDRESS OF THE FREE BLOCK. IF THE GETMAIN WAS
CONDITIONAL AND THERE WAS AN ERROR, AN ERROR CODE IS
PASSED BACK TO THE USER. IF THE GETMAIN WAS VARIABLE,
DMSSMN PROCEEDS AS ABOVE EXCEPT THAT IT SEARCHES THE
FREE CHAIN TO DETERMINE HOW MUCH STORAGE IS AVAILABLE
BEFORE CALLING THE GETBLK ROUTINE.
IF AN OS FREEMAIN IS ISSUED WITHOUT AN R OPERAND,
CONTROL IS PASSED VIA AN SVC5 TO THE SVC5 ENTRY POINT
IN DMSSMN. DMSSMN ROUNDS THE AMOUNT TO BE FREED UP TO
A DOUBLEWORD AND CALLS THE FREEBLK ROUTINE TO FREE THE
SPECIFIED STORAGE. CONTROL IS THEN RETURNED TO USER.
IF A CMS ROUTINE CALLS THE STORAGE INITIALIZATION
ROUTINE (STRINIT) IN DMSSMN, STRINIT
RESETS THE FREE STORAGE EXTENTS AND EFFECTIVELY FREES
ANY STORAGE THAT WAS PREVIOUSLY GETMAINED. IF ANY
ERRORS ARE ENCOUNTERED IN RESETTING THE EXTENTS AN
ABEND IS ISSUED, OTHERWISE CONTROL IS RETURNED TO THE
USER.
THE GETBLK ROUTINE IN DMSSMN SEARCHES THE FREE CHAIN
FOR A BLOCK OF FREE STORAGE LARGE ENOUGH TO MEET THE
CALLER'S NEEDS. WHEN IT FINDS ONE, IT EITHER RESETS
THE BLOCK LENGTH OR, IF ALL THE BLOCK IS NEEDED,
DELETES IT AND RETURNS CONTROL TO THE CALLER. IF A
LARGE ENOUGH BLOCK CANNOT BE FOUND AND THE GETMAIN IS
UNCONDITIONAL, AN ABEND IS ISSUED. IF A LARGE ENOUGH
BLOCK CANNOT BE FOUND AND THE GETMAIN WAS CONDITIONAL,
CONTROL IS RETURNED TO THE CALLER WITH AN ERROR CODE IN
REGISTER 15.
THE FREEBLK ROUTINE IN DMSSMN RETURNS A BLOCK OF
STORAGE TO THE FREE CHAIN. IF THE ADDRESS PASSED IT IS
BAD, THE FREEBLK ROUTINE ISSUES AN ABEND. IF THE BLOCK
IT IS FREEING IS CONTIGUOUS TO ANY OTHER FREE BLOCK IN
CORE, THE FREEBLK ROUTINE WILL COMBINE THE TWO BLOCKS.
UPON SUCCESSFUL COMPLETION CONTROL IS RETURNED TO THE
CALLER.
PREVIOUS STORAGE ALLOCATION REQUESTS MAINTAIN A
CHAIN OF POINTERS TO DISCONNECTED AREAS OF FREE CORE
EACH LINK +00 IS FREPTR - POINTER TO NEXT LINK
ZERO IF LAST IN CHAIN
+04 IS FRELEN - LENGTH OF FREE AREA
FRELST POINTS TO THE FIRST LINK IN THE CHAIN
OF DISCONNECTED AREAS
FSTFRE HOLDS THE ORIGINAL BEGINNING OF USER FREE STORAGE
LENFRE HOLDS THE LENGTH OF THAT AREA
NUCON LOCATION MAINHIGH HOLDS THE LOWER BOUND FOR EXTEND.
NUCON LOCATION FREELOWE (LOWEXT) HOLDS THE UPPER BOUND FOR
GETMAIN.
Calls to Other Routines
DMSSVT, DMSSAB,DMSFRE,DMSLGTA,DMSSLNAB