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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: STM32F4 Discovery, communication and libraries
Date: Fri, 29 Aug 2014 09:41:58 +0200
Organization: cbb software GmbH
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Date: 2014-08-29T09:41:58+02:00
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On Fri, 29 Aug 2014 00:17:12 +0300, Niklas Holsti wrote:

> On 14-08-28 23:09 , Dmitry A. Kazakov wrote:

>> You could not implement an equivalent of I/O queueing under the Ravenscar
>> constraints.
> 
> It is certainly possible to implement an I/O request queue in Ravenscar;
> I have done so for the platform SW on ESA's GOCE satellite. Multiple
> client tasks, one server (interface driver) task. An I/O request
> contains (or is, or refers to) a client-specific protected object (PO)
> with an "I/O completed" entry, on which the client task waits after
> enqueueing the I/O request. The server task processes submitted I/O
> requests in any order and concurrency it chooses; when an I/O request is
> done, the server task calls an operation on the request's PO, which
> unblocks the entry, resuming the client task.

Looks ugly to me. But I don't understand how the server's queue is accessed
by multiple tasks concurrently? And how could you cancel a pending request
in this schema?

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de