[Jack-Devel] JACK 2 is not real time safe on posix?

[Paul Davis]

On Sun, Apr 19, 2015 at 9:35 AM, Johannes Lorenz <
johannes89 at mailueberfall.de> wrote:

> > It's realtime safe as long as you know that those system calls pass
> > control to the thread you want them to pass control to and not some
> > other random thread that has nothing to do with JACK.
>
> Ok, but how does JACK keep the OS from executing a completely different
> process as the next job?
>

because the relevant threads in the server AND in the clients are all
scheduled in the SCHED_FIFO class, with (relatively) high priority.


>
> Also, as you say, by using e.g., malloc(), the realtime app indeed passes
> the control to the kernel thread, which has to do a lot with JACK (it does
> exactly what the rt app need to get process). So why is calling malloc()
> not realtime then?
>

**if** malloc() ends up with a call to the system call brk(), then the
kernel needs to memory allocation on behalf of the calling process. this is
not realtime safe.
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