Limit on file_sources in GRC?

GNU Radio
1

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
2

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.

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

3

On 23/06/12 14:00, Marcus D. Leech wrote:

With either of the source files, only, enabled in GRC, I can get that
The problem isn’t, per se, Gnu Radio. The semantics of opening for

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