Ah. Got it. Thanks.
CharlesSent from a mobile; please excuse the brevity. -------- Original message --------From: Walt Farrell <walt.farr...@gmail.com> Date: 9/13/17 3:59 PM (GMT+01:00) To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: CSST question On Wed, 13 Sep 2017 11:02:25 +0200, Charles Mills <charl...@mcn.org> wrote: >> Note that it says the store into the first operand will appear to occur >> before the store into >> the second operand, but it does NOT say that an observing CPU will see both >> stores or neither. > >Again, not arguing, just trying to fully understand. In your answer above, did >you consider this sentence from the PoOp description? > >"A serialization function is performed before the operation begins and again >after the operation is completed." Yes, I did. But as Binyamin says, you need to understand what CPU serialization entails. Again, I'm not an expert, but this is my interpretation: When you do something that serializes, the CPU ensures that all fetches and stores that have conceptually _completed_ by other CPUs are actually complete before you proceed. But CSST has two block-concurrent operations with a tiny window between the first store and the second store. Therefore, if a CSST occurs on a different CPU in theory your serialization coulde occur between the first and second store operations, and your serialization could complete and allow you to see the result of the first but not the second operation. -- Walt ---------------------------------------------------------------------- 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
