[linux-audio-dev] Audio/Midi system - RT prios..

[Paul Davis]

On Fri, 2005-12-30 at 17:17 +0100, Florian Schmidt wrote:
> On Fri, 30 Dec 2005 10:41:46 -0500
> Paul Davis <paul at linuxaudiosystems.com> wrote:
> 
> > several people have wanted JACK to export a thread create call that
> > would take care of the RT-ness. that way, if you can run JACK with RT
> > scheduling, you can run a MIDI thread too, with no extra steps. it would
> > also be useful for people doing FFT in JACK clients using a separate
> > thread.
> 
> actually, with realtime-lsm, there's really no need for this, except for
> some convenience. Every app can create its own RT threads these days.
> The 2.4.x capabilities days are (thank gawd) over :)

you don't know the correct priority to use. i imagine an api along the
lines of:

	jack_create_thread (pthread_t*, void* (thread_function)(void*), 
                            void* arg, int relative_to_jack);

the last argument would specify that the thread should run at, above or
below the jack RT thread(s) by a given amount. typical values would be 
+1, 0, -1 etc.

> > i don't agree with florian that the MIDI thread should run with higher
> > priority than the JACK watchdog, btw. i think the watchdog should be
> > higher than anything else until such a time as the kernel guarantees
> > "watchdog" functionality itself.
> 
> Agreed. why not make it prio 98 by default then? (system timer should
> still be higher i suppose). With a difference of only 10 between main
> jack loop and the watchdog, it might get a little crowded :)

good point.