[Tinyos-8051wg] Re: [Tinyos-2.0wg] Resource Allocation RoundRobinArbiter

[David Gay]

On 4/21/05, Kevin Klues <klues at tkn.tu-berlin.de> wrote:
> The Resource and the ResourceUser interfaces according to TEP108 have
> been committed to the interfaces directory.  The resource interface has
> changed slightly to include an event for when the bus is released.  I
> don't know how that wasn't included in the first place, but it cannot
> work properly without it.  This needs to be added into the TEP.

See comments below.

> A generic RoundRobinArbiter module providing the Resource and the
> ResourceUser interfaces has been implemented and committed to the sytems
> directory.  A test application for verifying that it works has been
> committed to the apps/TestArbiter directory.  It has only been tested on
> the eyesIFX nodes and needs verification on the telos and micas.

There's a problem with this implementation: it's not actually
implementing TEP 108. Specifically:

1) If the resource is available when you call request, you're supposed
to get a SUCCESS return and not get a granted event. The
implementation does signal granted in this case.

2) If the resource is not available when you call request, you're
supposed to eventually get a granted event (yes, this requires a queue
of pending requests). The implementation will never signal this.

3) The "released" event is not necessary if 2) is done according to the TEP...

4) request and release are async in the implementation, and not in the
TEP (I'm fairly sure we should change the TEP here).

So the basic question is: do we want to change the implementation, or
should we be changing the TEP? (i.e., does the TEP specify the wrong
thing? If so, we should have a discussion with the reasons...)

David Gay

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