Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.30-2

[Florian Schmidt]

On Tue, 23 Nov 2004 15:46:22 +0100
Ingo Molnar <mingo@xxxxxxx> wrote:

> i tried your new test-client, and i've got a generic question: should a
> jack client be able to generate an xrun via, other than via overloading
> jackd? E.g. i'm wondering about the following behavior: if start up
> jackd in the usual way:

The process() callback in a jackd client is run in a thread created by
libjack. This thread is run with SCHED_FIFO and at the same priority (or
one lower it seems) as the jackd server. Thus a client can only cause an
xrun when it takes a too long time to return from its process callback.

~$ ps  -C jackd -cmL
  PID   LWP CLS PRI TTY          TIME CMD
  975     - -     - ?        00:00:00 jackd
    -   975 TS   19 -        00:00:00 -
    -   976 TS   23 -        00:00:00 -
    -   977 FF  110 -        00:00:00 -
    -   978 FF  100 -        00:00:00 -

~$ ps -C jack_test -cmL
  PID   LWP CLS PRI TTY          TIME CMD
  988     - -     - pts/1    00:00:00 jack_test
    -   988 TS   20 -        00:00:00 -
    -   989 FF   99 -        00:00:00 -

So when you ctrl-z out of jack_test you cause its process() thread to be
suspended, too, thus jackd cannot finish processing its graph.

flo
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