164 lines
5.7 KiB
Plaintext
164 lines
5.7 KiB
Plaintext
;
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; File: DeferredTaskMgr.a
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;
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; Contains: Deferred Task Manager
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;
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; Written by: Gary Davidian
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;
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; Copyright: © 1986-1993 by Apple Computer, Inc. All rights reserved.
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;
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; Change History (most recent first):
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;
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; <SM6> 10/14/93 pdw Removing DTInstallHead routine - no longer needed and certainly
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; not wanted.
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; <SM5> 9/12/93 pdw Added DTInstallHead routine.
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; <SM4> 4/11/93 chp Modify DTInstall to run the specified task immediately if all
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; interrupts are already enabled and neither deferred tasks nor
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; VBL tasks are currently executing.
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; <SM3> 12/4/92 SWC Moved InitDTQueue here from StartInit.a.
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; <SM2> 5/21/92 kc Append "Trap" to the names of DTInstall,Enqueue and Dequeue to
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; avoid name conflict with the glue.
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; <1.2> 3/6/89 GGD Moved DisptchTsk from InterruptHandlers.a to DeferredTaskMgr.a
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; Re-Wrote DisptchTsk to remove windows where higher priority
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; interrupts doing DTinstall might be forgotten until the next
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; interrupt. Modified DTInstall to optimize for the success path.
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;
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;
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; This file contains the core routines pertaining to the Deferred Task Manager.
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;
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; The purpose of these routines is to allow lengthy interrupt tasks to be deferred
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; until all interrupts can be enabled. The interrupt handlers check the status of
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; the deferred task queue every time before exiting and dispatch queue tasks if the
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; interrupt mask is about to be restored to zero (all interrupts enabled).
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;
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; DTINSTALL installs a routine into the deferred task queue. There is one queue
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; maintained for all interrupt levels. A low memory variable, DTQueue, contains
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; the queue header.
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;
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; Tasks are removed from the queue automatically before they are dispatched by a
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; routine in the interrupt handling code.
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;
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; written by Rich Castro 23-November-86
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; re-written by Gary Davidian 4-March-89
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;
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PRINT PUSH, ON
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LOAD 'StandardEqu.d'
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INCLUDE 'HardwarePrivateEqu.a'
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PRINT POP
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MACHINE MC68020
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DTCORE PROC EXPORT
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EXPORT InitDTQueue, DTInstallTrap, DisptchTsk, vDisptch
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IMPORT InitQueue, ENQUEUETRAP, DEQUEUETRAP
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;_______________________________________________________________________
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;
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; Routine: InitDTQueue
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;
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; Arguments: none
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;
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; Function: called by the system init sequence in StartInit to
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; initialize the Deferred Task Manager queue
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;
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; Registers Used: A1
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;_______________________________________________________________________
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InitDTQueue LEA DTQueue,A1 ; init deferred task queue
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BSR.L InitQueue ; go do it
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LEA DTInstallTrap,A1 ; get ptr to deferred task install routine
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MOVE.L A1,jDTInstall ; and init jump vector to it
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RTS
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;_______________________________________________________________________
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;
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; Routine: DTINSTALL
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;
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; Arguments: A0 (input) : address of deferred task queue element
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; D0 (output): error code - 0 no error
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; -2 invalid queue element
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;
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; Function: Installs a deferred task queue element into the deferred
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; task queue pointed to by the low memory QHdr DTQueue.
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;
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; Format of the deferred task queue element is:
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;
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; DTLink Link to next queue element (pointer)
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; DTType element ID (word = DTQType)
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; DTFlags optional flags (word)
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; DTAddr address of deferred task routine (pointer)
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; DTParm optional A1 parameter (long)
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; DTReservd reserved for future use (long)
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;
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; Registers Used: D0,A1
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;_______________________________________________________________________
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DTInstallTrap
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CMP.W #DTQType,DTType(A0) ; is it the proper type?
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BNE.S TypeErr ; return error if not
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LEA DTQueue,A1 ; get ptr to queue
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JSR ENQUEUETRAP ; go add element
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; If a task is installed in the deferred task queue by non-interrupt code, <LW2>
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; it normally just sits there until an arbitrary time later when a system
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; interrupt occurs and causes it to be executed. This patch checks to see if
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; the interrupt mask is already zero and dispatches deferred tasks immediately
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; if it can.
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goToIt
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MOVE SR,D0
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ANDI.W #$0700,D0 ; test interrupt mask
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BNE.S @Defer ; if all interrupts are enabled:
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MOVEM.L A0-A3/D1-D3,-(SP) ; save regs normally saved by int handler
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JSR ([jDisptch]) ; dispatch deferred tasks immediately
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MOVEM.L (SP)+,A0-A3/D1-D3
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ANDI.W #$F8FF,SR ; reenable interrupts (disabled by dispatcher)
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@Defer
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MOVEQ.L #noErr,D0 ; no errors
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RTS ; return to caller
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TypeErr MOVEQ.L #VTypErr,D0 ; else flag the error
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RTS ; and return with error code in D0
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;______________________________________________________________________
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;
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; Dispatch routine for deferred tasks. This routine checks the deferred
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; task queue and removes and executes all tasks found. Regs D0-D3
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; and A0-A3 are saved prior to call.
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;
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;______________________________________________________________________
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DisptchTsk MOVE.L jDisptch,-(SP) ; get jump vector
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RTS ; and use it
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vDisptch BTST.B #INVBL,QFLAGS+VBLQUEUE ; doing VBL tasks?
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BNE.S @Exit ; if so, keep deferring
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BSET.B #InDTQ,DTQFlags ; already in dispatcher?
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BEQ.S @DspStart ; check the queue if not
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@Exit RTS ; otherwise exit
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@DspLoop MOVEA.L D0,A0 ; else setup ptr for use
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LEA DTQueue,A1 ; get ptr to queue
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JSR DEQUEUETRAP ; dequeue task to be executed
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MOVEA.L DTAddr(A0),A2 ; get ptr to first task
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MOVEA.L DTParm(A0),A1 ; get optional parameter
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ANDI.W #$F8FF,SR ; enable all ints
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JSR (A2) ; and go do task
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@DspStart ORI.W #HiIntMask,SR ; disable all ints
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MOVE.L DTskQHdr,D0 ; get queue head
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BNE.S @DspLoop ; loop if tasks exist
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BCLR.B #InDTQ,DTQFlags ; clear indicator
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RTS ; and exit
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END
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