If you want to load two doublewords, block concurrency guarantees each (aligned) doubleword is consistent, but if task 2 is in process of updating both doublewords, using (for example) LMG may result in you loading one doubleword from before task 2's change and one after.
-----Original Message----- From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf Of Keven Sent: Monday, January 14, 2019 16:54 To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Multi CPU interlock question Shouldn’t that be:Protection for readers is only necessary when the storage in question doesn’t cross a doubleword boundary? Keven On Mon, Jan 14, 2019 at 4:17 PM -0600, "Ngan, Robert" <rn...@dxc.com> wrote: Protection for readers is only necessary when the storage in question is larger than a doubleword. For quadwords, you can use either LPQ or PLO function 3 (CLX). Robert Ngan HCL Technologies -----Original Message----- From: IBM Mainframe Assembler List On Behalf Of Joe Owens Sent: Thursday, January 10, 2019 04:28 To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Multi CPU interlock question Yes, your illustration is exactly what I was concerned about. My instinct was CS was just about updaters of storage, and not readers, so there must be some other type of protection for readers. Thanks, Joe DXC Technology Company - Headquarters: 1775 Tysons Boulevard, Tysons, Virginia 22102, USA. DXC Technology Company -- This message is transmitted to you by or on behalf of DXC Technology Company or one of its affiliates. It is intended exclusively for the addressee. The substance of this message, along with any attachments, may contain proprietary, confidential or privileged information or information that is otherwise legally exempt from disclosure. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient of this message, you are not authorized to read, print, retain, copy or disseminate any part of this message. If you have received this message in error, please destroy and delete all copies and notify the sender by return e-mail. Regardless of content, this e-mail shall not operate to bind DXC Technology Company or any of its affiliates to any order or other contract unless pursuant to explicit written agreement or government initiative expressly permitting the use of e-mail for such purpose.