Help with understanding of shared memory read/write on Sequent

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2 total messages Started by Jaroslaw Nieplocha Tue, 29 Sep 1992 19:32

#430

Author: Jaroslaw Nieplocha
Date: Tue, 29 Sep 1992 19:32

17 lines
1290 bytes

I am wondering how Multiple-Reader-Single-Writer problem is
handled on the Sequent Symmetry depending on the data item size..

Let me explain the problem.
There are several processes reading data from a shared memory location.
Only one process writes data, item by item. There is no explicit
protection of the critical section. Assuming that the data item is  represented
by a floating point number, is it possible that readers may read corrupted
at bit or byte level data? What is the atomicity of read/write operations ?
Is it determined by the shared memory bus width (64bits) ?

Is there any Sequent publication which explains implementation of
shared memory read/write with respect to this issue?

Thanks for any help,

JN

Re: Help with understanding of shared memory read/write on Sequent

#436

Author: Simon Marshall
Date: Wed, 30 Sep 1992 09:44

25 lines
1428 bytes

In article <1992Sep29.193203.130065@ua1ix.ua.edu> lnieplo3@ua1ix.ua.edu (Jaroslaw Nieplocha) writes:
>There are several processes reading data from a shared memory location.
>Only one process writes data, item by item. There is no explicit
>protection of the critical section.

You might try:

@book {OSTERHAUG
       , author = "A. Osterhaug"  
       , title = "Guide to Parallel Programming on Sequent Computer Systems" 
       , publisher = "Prentice-Hall"
       , year = "1989"
       , series = "Sequent Technical Publications" 
       , address = "New Jersey, USA"
       , edition = "second"
}

To prevent concurrent modification to shared data, you could implement your own
lock, or use one of the Sequent's own (eg. m_lock()).

Simon.
-- 
Simon Marshall, Dept. of Computer Science, University of Hull, Hull HU6 7RX, UK
  "Football isn't about life and death.  It's more important than that." Bill
Email: S.Marshall@Hull.ac.uk    Phone: +44 482 465181    Fax: 466666   Shankley

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