Em Quinta 04 Maio 2006 03:54, Jan Kiszka escreveu:
>> ...
>> Yes, however I can't figure out how could I use mutexes as counting
>> semaphores, for instance. They have different meanings. However I could
>> think in semaphores protected by PIP in singular cases, although I
>> couldn't figure out how to do it in a systematic approach so that it could
>> be used in a realtime framework such as Xenomai...
>
>So you have to protect a multi-instance resource which can be used by a
>certain number of tasks in parallel? Is this a real scenario or just a
>hypothetical?
Just hypothetical for now. I guess I am preparing myself to the questions that
could arrive about Xenomai when presenting my master thesis (if I will
present it at all :) )
>Let's consider it's real: this means that every task successfully
>requesting the resource becomes one of the owners. So you would have to
>maintain a list of owners, not just a single reference as with mutexes.
Another way would be make Xenomai maintain this list of owners that would be
updated in rt_sem_p calls, doesn't it?
>Once someone requests the resource when there are no instances left, at
>least one of the owners should be boosted to the requesters priority.
Right.
>All feasible, but probably so special with traps and pitfalls (think of
>initialising or handling multiple requests by the same tasks)
I tried to, but couldn't figure out which would be those pitfalls.
>that no one yet developed a generic mechanism for any OS I know of. But you
>are always free to do so based on existing elementary mechanisms. :)
Maybe after my deadline ;)
Thank you,
Rodrigo.
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