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
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