[PD] Raspberry Pi & pd 0.46 with real time priority

[Miller Puckette]

Aha - I just tried Pd on a pi with recent raspian and... problems.  I'm in
the middle of waiting for a new compilation but I _think_ there are 2
problems happening at once:  first off, priority 98 (which Pd's watchdog
asks for) seems to be reserved for root.  I was able to get priority 96 with
no problem.  It looked like I had to either add the usual lines to
/etc/security/limits.conf:

* - rtprio 99
* - memlock 1000000000

(that's very permissive) or do the following:

chgrp audio pd/bin/pd pd/bin/pd-watchdog
chmod 2755 pd/bin/pd pd/bin/pd-watchdog

AND do one of the following: change the Pd source code, s_inter.c:

#ifdef USEAPI_JACK    
    p3 = (higher ? p1 + 7 : p1 + 5);
#else
    p3 = (higher ? p2 - 1 : p2 - 3);
#endif

to just:

    p3 = (higher ? p1 + 7 : p1 + 5);

(I still have to think about what level is really appropriate)

OR just compile with JACK support - that's why the "debs" worked, I think.
With JACK support Pd asks for a lower RT priority that the pi is willing to
give it.

More later...

Miller

On Wed, Dec 03, 2014 at 01:18:18PM +0100, katja wrote:
> On Wed, Dec 3, 2014 at 9:37 AM, IOhannes zmölnig <zmoelnig at iem.at> wrote:
> >
> >
> > Am 03. Dezember 2014 03:20:49 MEZ, schrieb katja <katjavetter at gmail.com>:
> >
> >>Following IOhannes' guidelines in an earlier thread I built the .deb
> >>packages from jessie source. That works great, but still it's quite a
> >>detour and in particular for new users there should be an easier way
> >>to get pd working properly on Raspberry Pi.
> >
> > How about making your .deb available via apt.puredata.info?
> 
> 
> A decent backport available from a logical place would be most
> convenient indeed. So far I was unable to build it with gpg
> verification. Also it's not a single .deb but a set of seven, which
> must be installed with dpkg. Package managers like apt-get, gdebi,
> Synaptic will pull 0.43 core, gui etcetera as puredata dependencies
> when you're on wheezy. This could probably be solved by editing
> dependency specs in debian/control, but still it would be confusing to
> have those .debs on the apt.puredata.info/releases list, since many
> people download from there manually. Maybe if there would be something
> like apt.puredata.info/backports/raspbian_wheezy?
> 
> There's no wheezy-backports in the Raspbian archive (due to lack of
> human resources). Raspbian maintainers try to stay close to wheezy but
> pull in from sid or make their own modifications if necessary
> (see:http://elinux.org/Raspbian). This brings me to another idea: if
> we (I mean Pd community) verify that puredata 0.46.2 is to be
> preferred over 0.43 for Raspberry Pi, they could pull in puredata
> 0.46.2 for wheezy. In the meantime could upload my unofficial backport
> somewhere to facilitate testing.
> 
> Katja
>