From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,956e1c708fea1c33 X-Google-Attributes: gid103376,public From: stt@houdini.camb.inmet.com (Tucker Taft) Subject: Re: Looking for implementation idea Date: 1999/02/08 Message-ID: #1/1 X-Deja-AN: 441901326 Sender: news@inmet.camb.inmet.com (USENET news) X-Nntp-Posting-Host: houdini.burl.averstar.com References: Organization: Intermetrics, Inc. Newsgroups: comp.lang.ada Date: 1999-02-08T00:00:00+00:00 List-Id: Corey Minyard (minyard@acm.org) wrote: : stt@houdini.camb.inmet.com (Tucker Taft) writes: : > : > I'm curious -- where did you get the impression that protected : > types did not work on a multiprocessor? I'm wondering how common : > is this misconception... : > : Thanks for the reply. I would expect the average programmer would : think of a protected type like a Java one, something more : semaphore-like. I knew that it wasn't (and I know the reasons), but I : would expect that when the average programmer puts something in a : protected type they would expect it to be "protected" by mutex, which : wouldn't happen on an SMP machine, but would on a uniprocessor one. I've lost you here. What "wouldn't happen on an SMP machine?" On an SMP operating system, O/S mutexes work across processors. : So should I now put spin-locks in all my protected type operations so : they will provide mutex on SMP machines (if mutex is what I am looking : for, which I expect is their most common use)? No, now I must have really confused you. The *implementation* of protected types generally uses spin locks on a multi-processor (though other mechanisms are also possible). The programmer need not worry about this at all: mutual exclusion is provided by protected types, even if there are multiple processors. : -- : Corey Minyard Internet: minyard@acm.org : Work: minyard@nortelnetworks.com UUCP: minyard@wf-rch.cirr.com -- -Tucker Taft stt@averstar.com http://www.averstar.com/~stt/ Technical Director, Distributed IT Solutions (www.averstar.com/tools) AverStar (formerly Intermetrics, Inc.) Burlington, MA USA