Type ASSEMBLE
Source Lines : 361
Fixes Applied : 0
Most Recent Version : Thursday, December 7, 1978
Last Fix ID : [Unmodified]
Module
DMTASK
Function
THE DMTASK MODULE IS THE SERVICE ROUTINE WHICH
CREATES NEW TASKS AND DELETES EXISTING TASKS
EXECUTED BY MSUP. THE ENTRY TO DMTASK IS BY MEANS
OF A BRANCH AND LINK FROM TASK PROGRAMMING. ANY
ENTRY TO DMTASK CAUSES THE CALLING TASK'S
EXECUTION TO BE SUSPENDED THROUGH THE FREEZE SVC
FUNCTION.
Attributes
REUSABLE, NON-INTERRUPTABLE
Operation
ON A REQUEST TO GENERATE A NEW TASK, DMTASK GETS
A SUPERVISOR STATUS QUEUE ELEMENT BY A CALL TO
DMTQRQ, BUILDS A NEW TASK ELEMENT FROM THE
INFORMATION PROVIDED BY THE CALLING TASK, FINDS
A ONE BYTE TASK ID WHICH IS NOT IN USE BY ANOTHER
TASK, AND ENQUEUES THE NEW TASK ELEMENT. WHEN
PROCESSING IS COMPLETE, DMTASK EXITS TO THE MSUP
DISPATCHER. SINCE THE NEW TASK IS INITIALIZED
DISPATCHABLE, THE NEW TASK CAN RECEIVE CONTROL
BEFORE THE CALLING (CREATING) TASK IS REDISPATCHED
ON RETURN FROM THE CREATE REQUEST.
ON A REQUEST TO TERMINATE A TASK, DMTASK BEGINS
BY SETTING THE "LIMBO" FLAG IN THE TASK ELEMENT OF
THE TASK TO BE TERMINATED, UNLESS THE TASK TO BE
TERMINATED IS THE SAME AS THE CALLING TASK.
SETTING OF THE "LIMBO" FLAG MARKS THE TASK AS
BEING PERMANENTLY NOT DISPATCHABLE. THE
TERMINATION PROCESSING CONTINUES BY THE PURGING OF
ALL INACTIVE I/O REQUESTS FOR THE TASK, ALL
ASYNCHRONOUS EXIT REQUESTS FOR THE TASK, AND ALL
PENDING GIVE REQUESTS FOR THE TASK. ALL PENDING
GIVE REQUESTS ADDRESSED TO THE TERMINATING TASK
ARE PURGED, AND EACH ASSOCIATED GIVE TABLE IS
POSTED WITH A X'FF' CODE. A SEARCH IS MADE FOR
ACTIVE I/O PROCESSING WHICH WAS INITIATED BY THE
TASK BEING TERMINATED; IF SUCH I/O IS FOUND,
PROCESSING IS TERMINATED AND CONTROL IS PASSED TO
THE DISPATCHER WITH AN ERROR RETURN CONTROL AND
THE TASK TO BE TERMINATED COMPLETELY DISABLED, BUT
STILL IN EXISTENCE. (IT IS THE RESPONSIBILITY OF
THE CALLING TASK TO CAUSE THE ACTIVE I/O TO BE
TERMINATED AND TO RETRY THE TERMINATE REQUEST.)
IF NO I/O IS ACTIVE FOR THE TERMINATING TASK, THE
MAIN STORAGE RESERVED BY THE TASK IS RELEASED, THE
TASK'S TASK ELEMENT IS DEQUEUED AND FREED BY A
CALL TO DMTQRQ, AND CONTROL IS RETURNED TO THE
DISPATCHER.
Calls to Other Routines
DMTQRQ - TO RESERVE AND RELEASE SUP QUEUE ELEMENTS