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From: Rosen.Adalog@wanadoo.fr (J-P. Rosen)
Subject: Re: Uninterruptible (atomic) operation?
Date: 1996/12/13
Message-ID: <58r1ed$lem@hetre.wanadoo.fr>#1/1
X-Deja-AN: 203873652
references: <9612111939.AA14087@most>
organization: Adalog
reply-to: Rosen.Adalog@wanadoo.fr
newsgroups: comp.lang.ada
Date: 1996-12-13T00:00:00+00:00
List-Id: <comp.lang.ada>


"W. Wesley Groleau (Wes)" <wwgrol@PSESERV3.FW.HAC.COM> wrote:

>2. An Ada 83 (which I'm stuck with) solution to (1) may not work if
>the reader and the writer are parts of independent Unix processes, and
>the shared object is created by system calls.  At first, I thought of
>the solution where the item shared is a pointer to the object, and
>the writer could overwrite the pointer atomically, after non-atomically
>updating/creating a new object.  Problem there is that the shared memory
>is guaranteed to be the same address for all processes using it.  But
>if it contains a pointer, the object pointed to in process X may be at
>a virtual address that is used for something else by process Y.

IF you are running on a mono-processor, you can have the update
done by a surrogate task that runs at highest priority level.
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