Re: [Discuss-gnuradio] tunnel.py buffer crash

[Eric Blossom]

On Wed, Mar 18, 2009 at 10:36:17PM -0700, yyzhuang wrote:
> 
> Hi Eric,
> 
> We read through the code. gr_buffer is a circular/ring buffer, so when
> reading/writing through it, we need to take modular into account. The assert
> error, it's line 125 in gr_buffer.h
> (gnuradio/gnuradio-core/src/lib/runtime/gr_buffer.h):
> 
>   unsigned
>   index_add (unsigned a, unsigned b)
>   {
>     unsigned s = a + b;
> 
>     if (s >= d_bufsize)
>       s -= d_bufsize;
> 
>     assert (s < d_bufsize);
>     return s;
>   } 
> 
> It is invoked by
> 
> void
> gr_buffer::update_write_pointer (int nitems)
> {
>   scoped_lock   guard(*mutex());
>   d_write_index = index_add (d_write_index, nitems);
> }
> 
> void
> gr_buffer_reader::update_read_pointer (int nitems)
> {
>   scoped_lock   guard(*mutex());
>   d_read_index = d_buffer->index_add (d_read_index, nitems);
> } 
> 
> I think it wants to add d_write_index or d_read_index by nitems. But when
> arrival rate is higher than service rate, buffer overflow occurs. Do you
> know how to increase the buffer size? Thanks.

The problem is most likely not in this code, but in a gr_block that is
misbehaving.  Increasing the buffer size will not fundamentally alter
the behavior. 

Eric