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

[John Shields]

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