aconnect occasionally causes kernel oopses

[folkert]

> > [ kernel bug if repeatingly aconnect'ing midi devices ]
> > 
> > > Does this happen if you do reconnect of kernel sequencer client?
> > > You can use snd-virmidi as well as snd-dummy.
> > > I'm asking it because it'll simplify the test a lot, which will be
> > > almost self-contained.
> > 
> > Like this?
> > 
> > root at lappiemctopface:~# aplaymidi -l
> >  Port    Client name                      Port name
> >  14:0    Midi Through                     Midi Through Port-0
> >  20:0    Virtual Raw MIDI 1-0             VirMIDI 1-0
> >  21:0    Virtual Raw MIDI 1-1             VirMIDI 1-1
> >  22:0    Virtual Raw MIDI 1-2             VirMIDI 1-2
> >  23:0    Virtual Raw MIDI 1-3             VirMIDI 1-3
> > 128:0    rtpmidi lappiemctopface          Network
> > 128:1    rtpmidi lappiemctopface          metronoom
> > 128:2    rtpmidi lappiemctopface          AppleMidi2IPMidiBridge
> > 128:3    rtpmidi lappiemctopface          oensoens
> > 130:0    FLUID Synth (11462)              Synth input port (11462:0)
> > 
> > and then:
> > 
> > root at lappiemctopface:~# cat test.sh 
> > while true
> > do
> > 	aconnect 20:0 21:0
> > 	aconnect -d 20:0 21:0
> > done
> > 
> > root at lappiemctopface:~# for i in `seq 0 3` ; do (./test.sh &) ; done
> > 
> > This hard locks-up my laptop: it doesn't even respond to capslock (led
> > on/off) anymore nor the ctrl+prtscr+alt+b combination.
> 
> Thanks, that's really helpful!
> I see the possible race now.

> Could you try the quick fix below?

Something may have changed:

folkert at oensoens:~$ aplaymidi -l
ALSA lib seq_hw.c:466:(snd_seq_hw_open) open /dev/snd/seq failed: Permission denied
Cannot open sequencer - Permission denied

???

Otoh it now runs fine from what I've could test.