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=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID, REPLYTO_WITHOUT_TO_CC 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: Corey Minyard Subject: Re: Looking for implementation idea Date: 1999/02/07 Message-ID: #1/1 X-Deja-AN: 442067891 Sender: minyard@wf-rch.cirr.com References: Organization: Wonderforce Research Reply-To: minyard@acm.org Newsgroups: comp.lang.ada Date: 1999-02-07T00:00:00+00:00 List-Id: stt@houdini.camb.inmet.com (Tucker Taft) writes: > : 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. > Thanks. That clears things up substantually! I thought that protected types were a priority-only thing, that they had no mutex built-in. They obviously still use priority, but are a more general purpose mutex. I guess I should have looked at the RM (9.5.1), it's pretty clear there. -- Corey Minyard Internet: minyard@acm.org Work: minyard@nortelnetworks.com UUCP: minyard@wf-rch.cirr.com