On Thursday, May 13, 2010, Chris Cannam wrote:
> On Thu, May 13, 2010 at 3:51 AM, Geoff King <[email protected]> wrote:
> > Hello,
> > I just found a bug that crashes rosegarden and locks up my system.
> > This happens when alsa seq is used with hrtimer setting in rosegarden.
> > This is on Fedora 12 w CCRMA rt kernel and rosegarden 10.04.2.  I had to
> > hit the reset button to get out of it.
> >
> > To make it happen:
> >
> > 1) start module snd_hrtimer
> > 2) start qjackctl/jackd running with midi driver set to SEQ.
> > 3) start rosegarden and go into preferences and change midi timer
> > preference from auto hrtimer.
> > 4) system locked up..
> >
> > Also locks up when starting rosegarden and these settings are saved.
>
> This sounds like a kernel bug rather than anything that Rosegarden can
> influence.  Changing the timer setting in Rosegarden just makes
> Rosegarden tell the ALSA kernel layer to use a different timer, it
> makes no other difference to Rosegarden's own behaviour.

It may be a kernel bug, but it is triggered by Rosegarden only, and not by 
other ALSA sequencer programs using this timer. For instance

1) start the module snd-hrtimer
2) start drumstick-sysinfo [1]. This program shows the hrtimer properties.
3) start drumstick-timertest. This program tests the best timer available, 
which is usually hrtimer.
4) If your ALSA drivers and library are modern enough (1.0.22 here), starting 
kmidimon, kmetronome, or kmid2 the system automatically selects hrtimer when 
it is available. This can be verified with this command while running the 
programs:

$ cat /proc/asound/seq/timer

> There is a long history of unstable interactions between RT kernel
> patches and the different ALSA sequencer timers.

I don't use a RT kernel, just the stock one provided by openSUSE, and 
Rosegarden consistently triggers the lockup.

Regards,
Pedro

[1] http://sf.net/projects/drumstick/

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