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Re: [Discuss-gnuradio] Gnuradio locking up

From: Matt Mills
Subject: Re: [Discuss-gnuradio] Gnuradio locking up
Date: Wed, 7 Dec 2011 09:31:58 -0700

Has anyone had time to look into the unlock() lockup that Rachel reproduced below further? I seem to be running into it left and right for some reason and sadly my C++ isnt anywhere near good enough to go seeking the cause myself.

On Tue, Nov 22, 2011 at 9:02 AM, Rachel Kroll <address@hidden> wrote:

On Nov 22, 2011, at 7:56 AM, Marcus D. Leech wrote:

> On 22/11/11 10:48 AM, Rachel Kroll wrote:
>> It's pretty easy to get wedged forever if you call lock and unlock a lot in conjunction with connect and disconnect.  Sooner or later, you'll hit a race and things will get stuck.
>> I have a simple reproduction case if anyone is interested.  It'll hang reliably after a few dozen iterations.
> That's the type of information that shouldn't be withheld from this
> list, and by implication, the
>  developers.  Don't assume that because you've found a
> bug/unexpected-behaviour, that the developers
>  know about it, and are working on a fix.

It's come up a few times in the mailing list archives.  The usual solution seems to be "add more sleeps", which of course is not a fix.

Anyway, here's the reproduction case:

#include <gnuradio/gr_file_sink.h>
#include <gnuradio/gr_sig_source_f.h>
#include <gnuradio/gr_hier_block2.h>
#include <gnuradio/gr_io_signature.h>
#include <gnuradio/gr_top_block.h>

static void connect(gr_top_block_sptr block, gr_sig_source_f_sptr source,
                   gr_hier_block2_sptr block2) {
 fprintf(stderr, "connect: calling lock, connect, unlock\n");
 block->connect(source, 0, block2, 0);
 fprintf(stderr, "connect: done\n");

static void disconnect(gr_top_block_sptr block, gr_sig_source_f_sptr source,
                      gr_hier_block2_sptr block2) {
 fprintf(stderr, "disconnect: calling block->lock\n");

 fprintf(stderr, "disconnect: calling block->disconnect\n");
 block->disconnect(source, 0, block2, 0);

 fprintf(stderr, "disconnect: calling block->unlock\n");
 block->unlock();                  // It usually hangs here.

 fprintf(stderr, "disconnect: done\n");

int main(int argc, char** argv) {
 // Inner block: block to sink.
 gr_hier_block2_sptr inner;
 inner = gr_make_hier_block2("inner",
                             gr_make_io_signature(1, 1, sizeof(float)),
                             gr_make_io_signature(0, 0, 0));

 gr_file_sink_sptr sink;
 sink = gr_make_file_sink(sizeof(float), "/dev/null");
 inner->connect(inner, 0, sink, 0);

 // Outer block: signal source to inner block.
 gr_top_block_sptr outer = gr_make_top_block("outer");
 gr_sig_source_f_sptr src = "" GR_COS_WAVE,
                                                 400, .1, 0);

 // Hook it up and get it going.
 connect(outer, src, inner);

 // Frob it until we die.
 while (true) {
   disconnect(outer, src, inner);
   fprintf(stderr, "\n\n------------------------\n\n");

   connect(outer, src, inner);

 return 0;

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