[Tinyos-devel] problem of using FTSP and CTP

[JeongGil Ko (John Ko)]

Hi.

Jong Hyun Lim and I have encountered the same problem with FTSP and CTP. 
Right now I hack CTP and make it try again with a retransmission timer 
when the sendResult is EBUSY. However fundamentally, the AMQueueImplP.nc 
should take care of such cases as Miklos discussed. If changes are made 
to CTP and not AMQueueImplP.nc all other protocols that use AMSender 
will have to deal with this corner case.

-John

Miklos Maroti wrote:
>> Packet senders shouldn't wire to ActiveMessageC.Send. It forces *all*
>> senders to handle EBUSY on a virtualized interface, adding unnecessary code.
>> It breaks scheduling fairness. The hack in 1.x to deal with this was a
>> global sendDone event; let's not go back down that path.
>>
>> Or is the issue that there should be a TEP saying that if anything in your
>> system uses AMSenderC.Send you MUST NOT wire to ActiveMessageC.Send?
>>     
>
> No, I think it should be spelled out that ActiveMessageC MAY return
> EBUSY even if you did not send a message.
>
> And of course then AMQueueImplP.nc needs to be fixed to handle this
> EBUSY return value and try it again (and not just give up sending a
> message). Then the problem is not at CTP at all, any other client
> would be suspect if used together with some other protocol that uses
> ActiveMessageC directly.
>
> Miklos
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>
>   

-- 
JeongGil (John) Ko
Ph.D. Student
Department of Computer Science
Johns Hopkins University
http://cs.jhu.edu/~jgko