-- Swapper>SwapperExceptionImpl.mesa (last edited by Knutsen on November 13, 1980 9:16 AM)

DIRECTORY

CachedRegion USING [Operation, Outcome],

Frame USING [Alloc, Free],

RuntimeInternal USING [MakeFsi],

SwapperException USING [],

SwapperPrograms USING [],

VM USING [PageNumber];

SwapperExceptionImpl: MONITOR

IMPORTS Frame, RuntimeInternal

EXPORTS SwapperException, SwapperPrograms =

BEGIN OPEN SwapperException;

QE: TYPE = RECORD [

pQEPrev: POINTER TO QE,

page: VM.PageNumber,

operation: CachedRegion.Operation,

outcome: CachedRegion.Outcome];

PQE: TYPE = POINTER TO QE;

fsiQE: CARDINAL = RuntimeInternal.MakeFsi[SIZE[QE]];

pQELast: PQE ← NIL; -- points to last of fifo queue of exception reports

report: CONDITION;

-- Instrumentation: (not necessary for operation)

currentExceptions, maxExceptions: CARDINAL ← 0;

Await: PUBLIC ENTRY PROCEDURE []

RETURNS [page: VM.PageNumber, operation: CachedRegion.Operation, outcome: CachedRegion.Outcome] =

BEGIN

pQE, pQENext: PQE;

WHILE pQELast=NIL DO WAIT report ENDLOOP; -- Wait for queue nonempty

-- Remove first report from queue and return it:

FOR pQE ← pQELast, pQE.pQEPrev WHILE pQE.pQEPrev~=NIL DO

pQENext ← pQE;

ENDLOOP;

[, page, operation, outcome] ← pQE↑;

IF pQE=pQELast THEN

pQELast ← NIL

ELSE

pQENext.pQEPrev ← NIL;

Frame.Free[pQE];

currentExceptions ← PRED[currentExceptions];

END;

Report: PUBLIC ENTRY PROCEDURE [page: VM.PageNumber, operation: CachedRegion.Operation, outcome: CachedRegion.Outcome] =

BEGIN

-- Add report to end of queue:

pQE: PQE = LOOPHOLE[Frame.Alloc[fsiQE], PQE];

currentExceptions ← SUCC[currentExceptions];

maxExceptions ← MAX[maxExceptions, currentExceptions];

pQE↑ ← [pQELast, page, operation, outcome];

pQELast ← pQE;

NOTIFY report

END;

END.

LOG

June 6, 1978 3:31 PMMcJonesCreated file (stub only).

July 31, 1978 10:53 AMMcJonesReplace stubs with real implementation.

April 28, 1980 10:18 AMForrestFrameOps => Frame.

November 13, 1980 9:16 AMKnutsenAdd instrumentation.