If the following store would cause an abend? On Tue, 12 Sep 2017 07:44:58 +0200 Charles Mills <charl...@mcn.org> wrote:
:>Not arguing at all, but what then is the point of CSST? What does CSST accomplish that could not more easily be done with CS/JNE/MVI or Store? :>Charles :>-----Original Message----- :>From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Greg Dyck :>Sent: Monday, September 11, 2017 2:54 PM :>To: IBM-MAIN@LISTSERV.UA.EDU :>Subject: Re: CSST question :>On 9/10/2017 11:39 AM, Charles Mills wrote: ... :>> Is that saying that there is a chance that another CPU might observe a :>> condition in which the store of the first operand had occurred, but :>> the store of the second operand had not? My understanding from earlier :>> paragraphs was that CSST happened "all at once" from the point of view :>> of other CPUs. Was I mistaken? :>Yes, it is saying that another CPU *might* observe the first store but not the second. As I read it, the POPs does *not* say that say CSST happens "all at once." It says that any fetches occur before a store occurs, and that each stores is block concurrent. If the compare is successful the processor will perform both stores. If the compare fails the processor will *not* perform both stores. :>The following from the POPs is important to consider with respect to usage of CSST- :> 3. The store value is intended to provide a separate :> “footprint” of the interlocked-update operation in :> a location apart from the first operand in a single :> unit of operation. :>The store into the second operand is a "footprint". CSST was not intended to be used as a means to atomically update two disparate storage locations. Rather, as a way to perform a Compare-and-swap operation, and set a footprint for recovery (ie, the CS completed) in non-shared storage associated with the current unit of work. -- 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
