iAPX 286 Operating System Writers Guide 1983

DATA SHARING, ALIASING, AND SYNCHRONIZATIONPL/M-286 COMPILER 961J-51J8 date PAGE 35657585961J61626364656667686971J717233222333322222221CALL NULLIFY(SLOT1);END;,IF SLOT2=SELECTOR$OF(NIL)THEN MESSAGE.DESCR2(2)=IJ; /* Mark as null */ELSE DO;CALL STORE DESCR(SLOT2,@MESSAGE.DESCR2);CALL DISABLE ALIAS PTR(SLOT2);CALL NULLIFY(SLOT2);END;DISABLE;CALL ENQUEUE MESSAGE(BOX ID, MSG PTR);CALL DEQUEUE-WAIT(BOX ID~@EXCEP);ENABLE; - -CALL DISPATCHER;RETURN;END SEND_MESSAGE;/*************************************************~*** **//* Receive Message from Mailbox */RECEivE_MESSAGE: PROCEDURE (BOX ID, MDATA PTR, SLOT1,SLOT2, EXCEP=P) PUBLIC-REENTRANT;732DECLARE BOX IDMDATA PTR(SLOTI, SLOT2)SELECTOR,POINTER,SELECTOR;742DECLARE EXCEP PEXCEP-BASED EXCEP PPOINTER,WORD;757677787981J81828384858687888991J9192939422222333332222333223DECLARE MSG PTR POINTER,MESSAGE BASED MSG PTR STRUCTURE(MESSAGE_FORMAT);CHECK MAIL:DISABLE;CALL DEQUEUE MESSAGE (BOX ID, @MSG PTR, @EXCEP);IF EXCEP=FAILED THEN /* No mail today */DO;CALL ENQUEUE WAIT (BOX_ID);ENABLE; -CALL DISPATCHER;GOTO CHECK MAIL;END; -ENABLE;/* Next statement may cause exception. */CALL MOVB(@MESSAGE.MDATA, MDATA PTR, MDATA SIZE);IF MESSAGE.DESCR1(2)1J /* Test-for null descriptor */THEN DO;CALL LOAD DESCR(@MESSAGE.DESCR1, SLOT1);CALL FIX_ALIAS_PTR(@MESSAGE.DESCR1);END;IF MESSAGE.DESCR2(2)1J /* Test for null descriptor */THEN DO;CALL LOAD_DESCR(@MESSAGE.DESCR2, SLOT2);Figure 5-7. Example of Mailbox Procedures (Cont'd.)5-15 121960-001