Linux signals and forks in GnuRadio

Are there any special considerations needed to use Linux signals
(in particular sigalarm) or forks from within a custom GnuRadio
C++ block?

Background information:

I’m written a block that consumes an HDLC/MPoFR bitstream and
extracts and forwards any contained IP packets. The block
generates a number of data and error statistics which I would
like to periodically send to another system via a UDP packet,
at a rate which is unrelated to the block’s sample rate.
My thought is to use alarm() to generate a sigalarm every
reporting interval, and register a private method as the
signal handler. If the reporting ends up taking too long,
I would use a fork from within the signal handler and do
the reporting in the child process.

Is this approach workable within the GnuRadio framework?
Or are there interactions with the scheduler and/or the
use of threads that render it unworkable or unreliable?

Thanks in advance!

@(^.^)@ Ed

On Fri, May 09, 2008 at 10:35:17AM -0400, Ed Criscuolo wrote:

like to periodically send to another system via a UDP packet,

Thanks in advance!

Hi Ed,

I’d stay away from signals and alarm. I think a “more likely to work
now and in the future” approach is to have the time keeping happen in
python, possibly in another thread, and have it call a method on your
class when it’s time to extract the results and send them via UDP.

FWIW, theads and signals are a fairly nasty combination. As you’ve
probably noticed, there’s only a single signal handler for all
threads, though you can mask which signals a given thread sees.
With the multi-processor (MP) scheduler I’m currently working on,
you’ll never know what thread could to executing any given block at
any given time.

Eric

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