Re: [Discuss-gnuradio] Limit on file_sources in GRC ?

On 23/06/12 14:00, Marcus D. Leech wrote:
>> Ubuntu 12.04 LTS, GNU Radio 3.6.1git-2-g2c7ea132 (on i7).
>>
>> I have a simple GRC flow with a couple of file sources - these are
>> FIFOs. I have a separate application which will simulate various
>> antenna configurations and it attempts to open both of these FIFOs in
>> O_WRONLY|O_NONBLOCK . As the FIFO's are Write, the other end needs to
>> be 'reading' in order that I don't get "No such device or address". I
>> accomplish this by starting the GRC flow.The separate application
>> attempts to open the FIFO's if unsuccessful 10 times.
>>
>> With either of the source files, only, enabled in GRC, I can get that
>> FIFO open first time from the application but cannot get them both to
>> open.
>>
>> Is there a limit on the # of file sources in GRC which is leading to
>> this behaviour?
>>
>> Kind Regards,
>>
>> John
>>
> The problem isn't, per se, Gnu Radio. The semantics of opening for
> write are such that there *must* be a reader available. Not so with
> opening for read, provided that you've opened NONBLOCK. Opening for
> read will block until there's a writer if it isn't opened NONBLOCK.
>
> So the problem is that you can't guarantee which *order* things will
> happen in -- that is, your opening for write may not correspond to the
> reader that Gnu Radio has opened (and is waiting to proceed). I'd
> say keep trying to open all of your writer FIFOs at once, and figure out
> which one(s) have succeeded. Pause a little between each iteration.
>
>
>>
>>
>>

Thanks Marcus - will give that a try. I was hoping I didn't need to send
data to the first FIFO opened so that the second one would/could succeed
so this is good news; 1 TPB helps, I guess.

Kind Regards,

John

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