[Tinyos-devel] Problem with ArbiterP - ResourceDefaultOwner.isOwner()

[Kevin Klues]

Hmmm... I'll need to look into this.  The read request shouldn't put
the arbiter into a state of RES_GRANTING right away, but rather queue
the request until the power manager has released it.  In this way, the
isOwner() command will return TRUE since the PowerManager is still the
owner and the arbiter is still in the RES_CONTROLLED state.  Like I
said, I need to take a look.

Kevin

On Nov 1, 2007 8:16 PM, Ken Bannister <regkb at deru.com> wrote:
> I have found an incompatibility with the latest change to ArbiterP's
> implementation of ResourceDefaultOwner.isOwner(). The issue occurs when
> trying to use a Sensirion Sht11 sensor with the SensirionSht11C component.
>
> The problem is a consequence of the wiring in HplSensirionSht11C. It
> allocates an FcfsArbiterC and wires
> SplitControlPowerManagerC.ResourceDefaultOwner to the Arbiter.
>
> When the higher level SensirionSht11C handles a read request it first
> requests the resource, which puts ArbiterP in RES_GRANTING state and then
> the ResourceDefaultOwner.requested() event is triggered. PowerManagerP's
> response eventually executes:
>
>    event void SplitControl.startDone(error_t error) {
>      if(call ResourceDefaultOwner.isOwner())
>        call ResourceDefaultOwner.release();
>    }
>
> At this point isOwner() returns false since it's no longer in RES_CONTROLLED
> state. I have worked around the problem by modifying the implementation of
> isOwner() to:
>
>      atomic
>      return state == RES_CONTROLLED
>              || (resId == default_owner_id
>                  && (state == RES_GRANTING || state == RES_IMM_GRANTING));
>
>
> There seems to be several scenarios when isOwner() is called, and I don't
> have the experience to suggest a more comprehensive solution.
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-- 
~Kevin