Re: [Discuss-gnuradio] shmat issue

[Philip Balister]

On 10/25/2010 07:36 PM, Joshua Lackey wrote:
> Quoting Philip Balister (address@hidden):
> > > On Wed, Oct 20, 2010 at 01:02:15PM -0400, Philip Balister wrote:
> > > > On 10/19/2010 10:51 PM, Eric Blossom wrote:
> > > > OK, it looks like x86 sets SHMLBA to PAGE_SIZE and arm uses 4 *
> > > > PAGE_SIZE. Need to puzzle through this a little more. This is the
> > > > failing check in the kernel.
> > >
> > > OK.  What's PAGE_SIZE on arm?
> >
> > PAGE_SIZE is still 4096, there is an additional restriction on the
> > address passed to shmat().
>
> Is the additional restriction '4 * PAGE_SIZE'?  If so, look in the
> circular_buffer.cc for kalibrate and change the line that reads:
>
>         m_pagesize = getpagesize();
>
> to
>
>         m_pagesize = 4 * getpagesize();
>
> It may be that easy.  The rest of the logic should work.

Basically, yes. Unfortunately, this didn't work. I'll double check when 
I get back from ELCE. It seems like the shm code returns an address that 
is not valid for using as an address you pass to shmat :(

> Alternatively, you can force the use of Posix shared memory and see if
> that works for kalibrate on your platform.  (The easiest thing to do
> would be to look for D_HOST_OSX and make sure those #ifdef's are the
> ones that gets compiled.)

I'll check this when I get home.

> Email me with your results and I'll add some code to make arm work in
> the next version of kal.

Thanks! Could we use the mmap code from gnuradio? That is what ends up 
being used there I think. I skimmed the shm code while working on this 
problem, and it looks like it used mmap internally :)

Philip