If you truly need a triple compare and swap then PLO will not help you. But if
you need a disjoint double compare and swap, you use the compare-and-swap
field as a counter and then you con do a compare swap and double store.
Example:
Fetch counter
A PLO compare-and-fetch value1
CC>0, go to A
PLO compare-and-fetch value 2
CC>0, go to A
calculate new value1 and 2
Add one to fetched counter
PLO CSDST fetched-counter new-fetched-counter, new value1, new-value2
CC>0, go to A
This requires that all processes that update value1 or value2 use PLO with the
same lock word.
On Sun, 3 Nov 2013 19:58:12 -0800 Jon Perryman <jperr...@pacbell.net> wrote:
:>I sure missed that one with the locks.
:>
:>PLO CDS does exactly what is wanted. It does 2 CS's within the locked
instruction.
:>
:>PLO CSDST on the other hand only does a single CS followed by 2 ST's. Since 3
separate load instructions (not under PLO control) are required when not in
contiguous storage, there is not any method that will guarantee the 3 values
are consistent with the others. A counter as suggested by Peter Relson won't
help either for this same reason.
:>
:>
:>I can't think of a situation where PLO CSDST is useful. Can anyone describe a
situation where it is useful?
:>
:>Jon Perryman.
:>
:>
:>
:>>________________________________
:>> From: Rob Scott <rsc...@rocketsoftware.com>
:>>
:>>
:>>
:>>I think the OP stated that his code could hold locks - in which case the
latch services cannot be used.
:>>
:>
:>----------------------------------------------------------------------
:>For IBM-MAIN subscribe / signoff / archive access instructions,
:>send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
--
Binyamin Dissen <bdis...@dissensoftware.com>
http://www.dissensoftware.com
Director, Dissen Software, Bar & Grill - Israel
Should you use the mailblocks package and expect a response from me,
you should preauthorize the dissensoftware.com domain.
I very rarely bother responding to challenge/response systems,
especially those from irresponsible companies.
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
