Re: [Discuss-gnuradio] Python-based sink block causes graph freeze under certain conditions

[Ethan Trewhitt]

Apologies - this bug has been found already:
http://gnuradio.org/redmine/issues/594

I tracked down the freeze to the "unlock()" call in selector.py, which
led me to the bug report. Hope it gets fixed soon :)

Until then, no graph changes!

On Wed, Sep 25, 2013 at 5:08 PM, Ethan Trewhitt <address@hidden> wrote:
> I created a Python-based sink block that works well in most cases. I
> started having problems when I created a GUI checkbox (using GRC) to
> control a Selector or Valve block in a separate subgraph. As soon as I
> change the checkbox, the whole graph freezes.
>
> So far I have tracked this down to the Python sink block. I grabbed
> one of the built-in blocks and build a test that demonstrates the
> problem in the simplest way. The graph looks like this (there are two
> separate subgraphs):
>
> Subgraph 1:
> Constant Source #1 -> Throttle -> Python test sink
>
> Subgraph 2:
> Constant Source #2 -> Selector -> Throttle -> Null sink
> Constant Source #3 -> ^           (points to the selector, also)
>
> The checkbox switches the selector between Constant Source #2 and #3.
> Whenever the Python test sink is part of the upper graph, switching
> the lower graph (using the checkbox) causes everything to freeze.
>
> Debugging steps:
>
> I ran this graph via GDB and watched threads being created/destroyed.
> Whenever the checkbox is changed, a bunch of threads are killed. I'm
> guessing this is GR shutting down a bunch of blocks and trying to
> restart them with different connections, but something in the Python
> block isn't getting shut down, so everything stalls.
>
> In the code below, if you replace the reference to "self.sink" with
> "self.blocks_null_sink_1" in the connection setup, the problem goes
> away.
>
> Here's the code:
>
>
> #!/usr/bin/env python
>
> from gnuradio import blocks
> from gnuradio import gr
> from gnuradio.wxgui import forms
> from grc_gnuradio import blks2 as grc_blks2
> from grc_gnuradio import wxgui as grc_wxgui
> import numpy
>
> import wx
>
> class sink_test(grc_wxgui.top_block_gui):
>
>     def __init__(self):
>         grc_wxgui.top_block_gui.__init__(self, title="Sink Test")
>         self.check = check = True
>
>         ##################################################
>         # Blocks
>         ##################################################
>         self._check_check_box = forms.check_box(
>             parent=self.GetWin(),
>             value=self.check,
>             callback=self.set_check,
>             label="check",
>             true=True,
>             false=False,
>         )
>         self.Add(self._check_check_box)
>         self.const_source_x_0_1 = gr.sig_source_c(0, gr.GR_CONST_WAVE, 0, 0, 
> 12)
>         self.const_source_x_0_0 = gr.sig_source_c(0, gr.GR_CONST_WAVE, 0, 0, 
> 0)
>         self.const_source_x_0 = gr.sig_source_f(0, gr.GR_CONST_WAVE, 0, 0, 0)
>         self.blocks_throttle_0 = blocks.throttle(gr.sizeof_float*1, 1000)
>         self.blocks_throttle_1 = blocks.throttle(gr.sizeof_gr_complex*1, 1000)
>         self.blocks_null_sink_0 = blocks.null_sink(gr.sizeof_gr_complex*1)
>         self.blocks_null_sink_1 = blocks.null_sink(gr.sizeof_float*1)
>      # not used by default. enable by connecting below
>         self.blks2_selector_0 = grc_blks2.selector(
>             item_size=gr.sizeof_gr_complex*1,
>             num_inputs=2,
>             num_outputs=1,
>             input_index=0 if check else 1,
>             output_index=0,
>         )
>         self.sink = test_sink()
>
>         ##################################################
>         # Connections
>         ##################################################
>         self.connect((self.const_source_x_0, 0), (self.blocks_throttle_0, 0))
>         self.connect((self.blocks_throttle_0, 0), (self.sink, 0))
>    # change this from self.sink to self.blocks_null_sink_1 to see the
> problem go away
>         self.connect((self.const_source_x_0_0, 0), (self.blks2_selector_0, 1))
>         self.connect((self.blks2_selector_0, 0), (self.blocks_throttle_1, 0))
>         self.connect((self.blocks_throttle_1, 0), (self.blocks_null_sink_0, 
> 0))
>         self.connect((self.const_source_x_0_1, 0), (self.blks2_selector_0, 0))
>
>
>     def get_check(self):
>         return self.check
>
>     def set_check(self, check):
>         self.check = check
>         self._check_check_box.set_value(self.check)
>         self.blks2_selector_0.set_input_index(int(0 if self.check else 1))
>
> # Python block
> class test_sink(gr.sync_block):
>     def __init__(self):
>         gr.sync_block.__init__(
>             self,
>             name = "test_sink",
>             in_sig = [numpy.float32],
>             out_sig = None,
>         )
>         self.key = None
>
>     def work(self, input_items, output_items):
>         return len(input_items[0])
>
> if __name__ == '__main__':
>     tb = sink_test()
>     tb.Run(True)