iAPX 286 Operating System Writers Guide 1983

DATA SHARING, ALIASING, AND SYNCHRONIZATIONPL/M-286 COMPILER 960-508 date PAGE 2293031323334353637383912212212211FREE MSG SPACE: PROCEDURE(BOX ID,MSG PTR) EXTERNAL;DECLARE-BOX ID SELECTOR, -MSG-PTR POINTER;END FREE_MSG=SPACE;ENQUEUE MESSAGE: PROCEDURE(BOX ID, MSG_PTR) EXTERNAL;DECLARE BOX ID SELECTOR, -MSG PTR POINTER;END ENQUEUE_MESSAGE;DEQUEUE_MESSAGE: IlROCEDURE(BOX_ID, MSG P P, EXCEP P)EXTERNAL;DECLARE BOX ID SELECTOR, (MSG P P, EXCEP_P) POINTER;END DEQUEUE_MESSAGE; - -/*******************************************************//* Mailbox Data Structures */DECLARE MDATA SIZE LITERALLY 146 I ;DECLARE MESSAGE FORMAT LITERALLY, MDATA-(MDATA SIZE) BYTE,-DESCRl (4 )WORD,DESCR2 (4 ) WORD' ;/*******************************************************//* Send Message via Mailbox */401SEND MESSAGE:PROCEDURE(BOX ID, MDATA PTR, SLOT1, SLOT2,EXCEP _P) PUBLIC REENTRANT;412DECLARE BOX IDSELECTOR,MDATA PTR POINTER,(SLOTl, SLOT2) SELECTOR;422DECLARE EXCEP PEXCEP- BASED EXCEP PPOINTER,WORD;434445464748495051525354552222333222233DECLARE MSG PTR POINTER,MESSAGE BASED MSG PTR STRUCTURE(MESSAGE_FORMAT);CALL GET MSG SPACE(BOX ID, @MSG PTR, @EXCEP);IF EXCEP=FAILED THEN /* the box-is full of messages */DO;CALL DISPATCHER;RETURN;END;/* The next statement will cause an exception if thesegment containing the data is not present.Therefore interrupts are enabled. */CALL MOVB (MDATA PTR,@MESSAGE.MDATA,MDATA SIZE);IF SLOT1=SELECTOR$OF (NIL) -THEN MESSAGE.DESCR1(2)=0; /* Mark as null */ELSE DO;CALL STORE DESCR(SLOT1,@MESSAGE.DESCR1);CALL DISABLE_ALIAS_PTR(SLOT1);Figure 5·7. Example of Mailbox Procedures (Cont'd.)5-14 121960-001