Re: [Rosegarden-devel] JACK

[David O. <da...@ol...>]

On Wednesday 19 February 2003 01.17, Silvan wrote:
> On Tuesday 18 February 2003 04:41 pm, David Olofson wrote:
> > > If it can't run well enough to be
> > > functional as a user, then I won't run it.
> >
> > Of course. If it's *that* bad, it's useless and must be fixed.
> > That's all there is to it.
>
> Well, then Jack is useless...  I get so many xruns with it that
> it's pointless to bother starting the thing.

Of course. It *requires* hard real time scheduling for low latency=20
work, just like any RT application. There's no way around that, and=20
the only thing that makes JACK more sensitive than most other RT=20
audio apps is the out-of-process model. (The alternative is the=20
Win32/Mac OS ReWire variant, where the DSP portion of apps run in the=20
same process, like traditional plugins.)


[...]
> > proper watchdog in a separate process, *will* work. All we need
> > is a way to completely avoid running JACK as root - and the only
> > missing piece is mlock() of another process.
>
> Call me when kernel 2.8.20 is ready, then we'll talk about it
> again.  :)

Well, one would hope this is fixed before 2.5.x becomes 2.6 or 3.0 or=20
whatever. I don't think it's acceptable that something that *could*=20
be completely safe isn't, for a reason like this. Why is allowing=20
root to make any process SCHED_FIFO considered safe, while mlock()ing=20
another process is not? Both can kill the system of the root process=20
is compromized, and both could be made safe.

Oh well... Maybe someone actually has to *implement* it? :-)


Wait... If memory is *shared*, only one process has to lock it.=20
Problem is that you'd have to do it with the code and stack as well,=20
and I can't think of any straightforward way of doing that.

Will think more about this. Ideas are wellcome.


//David Olofson - Programmer, Composer, Open Source Advocate

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