First, I'm not sure why you have chosen PLT as your lock word. It's very important the lock word resolve to the same REAL address no matter where the PLO executes. Since you are talking about multiple operations against the same chain, unless all the processes exist in the same shared program you can't be sure the same lock word is always used. The lock word contents are not altered just used to create a lock value(PLT) for serialization. From your code, I would chose CSAMSEGF.
Second, you can't mix the CDS with PLO and expect consistent results. It would be very easy to convert the CDS to a PLO Compare Double and Swap (compare each full word and swap). Just be sure to use the same lock word which I still suggest as CSAMSEGF. Third, you're going to have to use a count. And since you are acquiring and releasing this storage, you REALLY have to use a counter. Just add a full word counter in CSA. In this case, I would choose the counter as the lock word. As long as you have a full word counter and recovery to treat a 0c4 as a re-drive (see my prior comments), this should work. I don't know if you can, but the choice of another methodology where storage is not acquired for each add and released for each delete would be recommended. However, you can make this work but not without a counter. Last, Peter's comment is very valid. Read the notes in CDS in the POM. I don't know why PLO doesn't reference them since they are just as applicable to PLO. I have not closely examined your logic so I don't know what the logic problem is in the code. I'm just commenting on the methodology. Kenneth -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Donald Likens Sent: Friday, November 08, 2013 10:22 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Serialization without Enque Thank You for your help (all of you) but Peter's statement below does not make sense to me (maybe because I don't understand something). The reason that the free queue protocol needs a sequence number is because even if the header "matches", the values that you need to put into your new element for the "next" and/or "previous" may no longer be correct due to a set of additional asynchronous operations. I use PLO to add an element to a chain. The chain only has forward pointers. I always add to the end of the chain. I use storage (not CPOOL) to get the element. It turns out that I haven't gotten the PLO instruction to work properly yet but in theory in my scenario it seem to me that if the pointer to the last element is pointing to a element (Not 0) I should be able to store the next pointer and the last pointer in one PLO CSDST. Here is the actual (not working code... It is not updating the chain properly): CSAMSEGL <== Last element on the chain CSAMSEGF <== First element on the chain R8 Address of element to add. MSEGNEXT <== Pointer to next element in last control block MSEGCB <== element name DOX078 DS 0H *C IF CSAMSEGL EQ 0 THEN (no elements on the chain) XR R4,R4 XR R5,R5 LR R2,R8 (R8: ADDRESS OF MSEGCB) LR R3,R8 *C SET CSAMSEGL = CSAMSEGF = MSEGCB JUST BUILT CDS R4,R2,CSAMSEGF IF CSAMSEGF & CSAMSEGL = 0, STM 2,3,CSAMSEGF BC 4,ELIFX076 *C ELSE B EIFX076 ELIFX076 DS 0H *C IF CSAMSEGL = CSAMSEGL (R2) *C SET CSAMSEGL = POINTER_TO_NEW_MSEG (R8) *C SET MSEGNEXT = POINTER_TO_NEW_MSEG (R8) CSDST EQU 16 L R2,CSAMSEGL LA R0,CSDST LA R1,PLT LR R3,R8 LA R4,CSAMSEGL CSAMSEGL IS IN CSA ST R4,OPERAND6 LA R4,MSEGNEXT MSEGNEXT IS IN CSA ST R4,OPERAND4 ST R8,OPERAND3 ST R8,OPERAND5 PLO R2,CSAMSEGL,0,PL * THE FIRST-OPERAND COMPARISON VALUE AND THE SECOND OPERAND ARE * COMPARED. IF THEY ARE EQUAL, THE FIRST-OPERAND REPLACEMENT VALUE * IS STORED AT THE SECOND-OPERAND LOCATION, AND THE THIRD OPERAND IS * STORED AT THE FOURTHOPERAND LOCATION. THEN, THE FIFTH OPERAND IS * STORED AT THE SIXTH-OPERAND LOCATION. BNZ DOX078 EIFX076 DS 0H PLT DS D PLO LOCK TOKEN PL DS 0F PARAMETER LIST ORG PL+60 OPERAND3 DS A NEW MSEG ADDRESS ORG PL+76 OPERAND4 DS A ADDRESS OF CSAMSEGL ORG PL+92 OPERAND5 DS A NEW MSEG ADDRESS ORG PL+108 OPERAND6 DS A ADDRESS OF MSEGNEXT ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
